@article{murtazoev_berdonosov_lyssenko_dolgikh_geidorf_volkova_koo_whangbo_vasiliev_2023, title={A cascade of magnetic phase transitions and a 1/3-magnetization plateau in selenite-selenate Co-3(SeO3)(SeO4)(OH)(2) with kagome-like Co2+ ion layer arrangements: the importance of identifying a correct spin lattice}, ISSN={["1477-9234"]}, DOI={10.1039/d3dt01620j}, abstractNote={Co 3 (SeO 3 )(SeO 4 )(OH) 2 has kagomé-like layers of Co 2+ ions. It undergoes magnetic transitions at 27.5, 19.4 and 8.1 K, and exhibits a 1/3-magnetization plateau. The H – T diagram shows an antiferromagnetic phase I and ferrimagnetic phases II and III.}, journal={DALTON TRANSACTIONS}, author={Murtazoev, A. F. and Berdonosov, P. S. and Lyssenko, K. A. and Dolgikh, V. A. and Geidorf, M. Y. and Volkova, O. S. and Koo, H. -J and Whangbo, M. -H and Vasiliev, A. N.}, year={2023}, month={Jun} }
 @article{o'donnell_gabilondo_jana_koldemir_block_whangbo_kremer_pottgen_maggard_2023, title={Cation exchange route to a Eu(II)-containing tantalum oxide}, volume={328}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2023.124338}, abstractNote={Traditional synthetic efforts to prepare Eu(II)-containing oxides have principally involved the use of high temperature reactions starting from EuO or a controlled, highly-reducing, atmosphere. Conversely, chimie douce approaches that are more amenable to the targeted syntheses of new, and potentially metastable, Eu(II)-oxides have yet to be explored. Herein, a cation-exchange route to new Eu(II)-containing oxides, e.g., EuTa4-xO11 (x = 0.04), has been discovered and its structure determined by powder X-ray diffraction (Space group P6322 (#182), a = 6.2539(2) Å; c = 12.3417(2) Å). The compound derives from the cation exchange of Na2Ta4O11, via a reaction with EuBr2 at 1173 K, and replacement by half the number of divalent Eu cations. Rietveld refinements show preferential ordering of the Eu cations over one of the two possible cation sites, i.e., Wyckoff site 2d (∼94%; Eu1) versus 2b (∼6%; Eu2). Total energy calculations confirm an energetic preference of the Eu cation in the 2d site. Tantalum vacancies of ∼1% occur within the layer of Eu cations and TaO6 octahedra, and ∼20% partial oxidation of Eu(II) to Eu(III) cations from charge balance considerations. 151Eu Mössbauer spectroscopy measured at 78K found an Eu(II):Eu(III) ratio of 69:31, with a relatively broad line width of the former signal of Γ = 7.6(2) mm s–1. Also, the temperature-dependent magnetic susceptibility could be fitted to a Curie Weiss expression, giving a μeff = 6.2 μB and θCW = −10K and confirming a mixture of Eu(II)/Eu(III) cations. The optical bandgap of EuTa4-xO11 was found to be ∼1.5 eV (indirect), significantly redshifted as compared to ∼4.1 eV for Na2Ta4O11. Spin-polarized electronic structure calculations show that this redshift stems from the addition of Eu 4f7 states as a higher-energy valence band. Thus, these results demonstrate a new cation-exchange approach that represents a useful synthetic pathway to new Eu(II)-containing oxides for tunable magnetic and optical properties.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={O'Donnell, Shaun and Gabilondo, Eric and Jana, Subhendu and Koldemir, Aylin and Block, Theresa and Whangbo, Myung-Hwan and Kremer, Reinhard and Pottgen, Rainer and Maggard, Paul A.}, year={2023}, month={Dec} }
 @article{ouyang_shi_su_cheng_gao_jia_whangbo_ren_2023, title={Magnetic transitions of hydrogenated H (x) CrO2 (x=0-2) monolayer from a ferromagnetic half-metal to antiferromagnetic insulator}, volume={35}, ISSN={["1361-648X"]}, DOI={10.1088/1361-648X/acccc6}, abstractNote={Abstract Two-dimensional (2D) transition metal oxide monolayers are currently attracting great interest in materials research due to their versatility and tunable electronic and magnetic properties. In this study, we report the prediction of magnetic phase changes in H x CrO 2 (0 ⩽ x ⩽ 2) monolayer on the basis of first-principles calculations. As the H adsorption concentration x increases from 0 to 0.75, H x CrO 2 monolayer transforms from a ferromagnetic (FM) half-metal to a small-gap FM insulator. When x = 1.00 and 1.25, it behaves as a bipolar antiferromagnetic (AFM) insulator, and eventually becomes an AFM insulator as x increases further up to 2.00. The results suggest that the magnetic properties of CrO 2 monolayer can be effectively controlled by hydrogenation, and that H x CrO 2 monolayers have the potential for realizing tunable 2D magnetic materials. Our results provide a comprehensive understanding of the hydrogenated 2D transition metal CrO 2 and provide a research method that can be used as a reference for the hydrogenation of other similar 2D materials.}, number={30}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Ouyang, Wenbin and Shi, Bowen and Su, Tianhao and Cheng, Xuli and Gao, Heng and Jia, Fanhao and Whangbo, Myung-Hwan and Ren, Wei}, year={2023}, month={Aug} }
 @article{cheng_deng_yao_guo_whangbo_ding_2023, title={Phase Competition and Strong SHG Responses of the (Li2MMSe4)-M-II-Se-IV Family: Atom Response Theory Predictions versus Experimental Results}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.2c03151}, abstractNote={Compounds of diamond-like (DL) structures are one of the important systems in searching for new high-performance infrared nonlinear optical (IR NLO) materials. However, the phase competition of the diverse DL allotropes and the origin of the SHG response at the atom and orbital level for these NLO materials remain an unsolved hot topic. In this work, the atom response theory (ART) combined with the hybrid density functional calculations was applied to explore the NLO properties of the Li2MIIMIVSe4 (MII = Zn, Cd, Hg; MIV = Si, Ge, Sn) family. Twenty-three new promising IR NLO compounds were predicted with a wide range of band gaps (1.79–3.62 eV), high SHG responses (∼0.7 to 2.5 × AGS), moderate birefringences (∼0.04), and possibly high LIDT (laser-induced damage threshold) values. Among them, Li2HgGeSe4 and Li2HgSnSe4 with the Pna21 structure were experimentally confirmed very recently. The phase competition and the order of band gaps of these compounds were explained from the viewpoint of the crystal structure and chemical bonding. Our ART analyses showed that the large NLO coefficients of these selenides arise mainly from the Se-4p orbitals (∼76%) while the anomaly low contribution of Hg is attributed to the tiny d–p covalent interactions. The SHG responses of all structures were rationalized by the deffp vs αsum/(NEg) linear relationship, showing the importance of this relation in designing and synthesizing new NLO materials.}, journal={CHEMISTRY OF MATERIALS}, author={Cheng, Xiyue and Deng, Shuiquan and Yao, Wen-Dong and Guo, Sheng-Ping and Whangbo, Myung-Hwan and Ding, Bohan}, year={2023}, month={Jan} }
 @article{moskin_kozlyakova_chung_koo_whangbo_vasiliev_2023, title={Successive Short- and Long-Range Magnetic Ordering in Ba2Mn3(SeO3)(6) with Honeycomb Layers of Mn3+ Ions Alternating with Triangular Layers of Mn2+ Ions}, volume={16}, ISSN={["1996-1944"]}, DOI={10.3390/ma16072685}, abstractNote={Mixed-valent Ba2Mn2+Mn23+(SeO3)6 crystallizes in a monoclinic P21/c structure and has honeycomb layers of Mn3+ ions alternating with triangular layers of Mn2+ ions. We established the key parameters governing its magnetic structure by magnetization M and specific heat Cp measurements. The title compound exhibits a close succession of a short-range correlation order at Tcorr = 10.1 ± 0.1 K and a long-range Néel order at TN = 5.7 ± 0.1 K, and exhibits a metamagnetic phase transition at T < TN with hysteresis most pronounced at low temperatures. The causes for these observations were found using the spin exchange parameters evaluated by density functional theory calculations. The title compound represents a unique case in which uniform chains of integer spin Mn3+ (S = 2) ions interact with those of half-integer spin Mn2+ (S = 5/2) ions.}, number={7}, journal={MATERIALS}, author={Moskin, Artem and Kozlyakova, Ekaterina and Chung, Seung Hwan and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Vasiliev, Alexander}, year={2023}, month={Apr} }
 @article{li_deng_whangbo_luo_2022, title={<p>Orbital projection technique to explore the materials genomes of optical susceptibilities & nbsp;& nbsp;</p>}, volume={12}, ISSN={["2158-3226"]}, DOI={10.1063/5.0067891}, abstractNote={The development in materials science and pharmaceutics shows that there exist some key materials genomes, i.e., certain groups of atoms with specific constituents and structures, which govern the property of a series of materials based on them. To pinpoint such materials, genomes are helpful to assemble functional units and synthesize new materials and, thus, have a profound meaning. In this work, we develop an innovative method based on the idea of projecting atomic orbitals’ wavefunction, which enables us to project every physical quantity into their orbital contribution and, thus, can be widely used to identify the materials genomes of various properties. Within this framework, we derive the expressions of the projected optical susceptibilities and exhibit a paradigm of studying the corresponding materials genomes of optical properties, especially the desired nonlinear optical materials.}, number={5}, journal={AIP ADVANCES}, author={Li, ZhenHua and Deng, Shuiquan and Whangbo, Myung-Hwan and Luo, Hong-Gang}, year={2022}, month={May} }
 @article{whangbo_koo_bruecher_puphal_kremer_2022, title={Absence of Spin Frustration in the Kagome Layers of Cu2+ Ions in Volborthite Cu3V2O7(OH)(2)center dot 2H(2)O and Observation of the Suppression and Re-Entrance of Specific Heat Anomalies in Volborthite under an External Magnetic Field}, volume={7}, ISSN={["2410-3896"]}, DOI={10.3390/condmat7010024}, abstractNote={We determined the spin exchanges between the Cu2+ ions in the kagomé layers of volborthite, Cu3V2O7(OH)2·2H2O, by performing the energy-mapping analysis based on DFT+U calculations, to find that the kagomé layers of Cu2+ ions are hardly spin-frustrated, and the magnetic properties of volborthite below ~75 K should be described by very weakly interacting antiferromagnetic uniform chains made up of effective S = 1/2 pseudospin units. This conclusion was verified by synthesizing single crystals of not only Cu3V2O7(OH)2·2H2O but also its deuterated analogue Cu3V2O7(OD)2·2D2O and then by investigating their magnetic susceptibilities and specific heats. Each kagomé layer consists of intertwined two-leg spin ladders with rungs of linear spin trimers. With the latter acting as S = 1/2 pseudospin units, each two-leg spin ladder behaves as a chain of S = 1/2 pseudospins. Adjacent two-leg spin ladders in each kagomé layer interact very weakly, so it is required that all nearest-neighbor spin exchange paths of every two-leg spin ladder remain antiferromagnetically coupled in all spin ladder arrangements of a kagomé layer. This constraint imposes three sets of entropy spectra with which each kagomé layer can exchange energy with the surrounding on lowering the temperature below ~1.5 K and on raising the external magnetic field B. We discovered that the specific heat anomalies of volborthite observed below ~1.5 K at B = 0 are suppressed by raising the magnetic field B to ~4.2 T, that a new specific heat anomaly occurs when B is increased above ~5.5 T, and that the imposed three sets of entropy spectra are responsible for the field-dependence of the specific heat anomalies.}, number={1}, journal={CONDENSED MATTER}, author={Whangbo, Myung-Hwan and Koo, Hyun-Joo and Bruecher, Eva and Puphal, Pascal and Kremer, Reinhard K.}, year={2022}, month={Mar} }
 @article{koo_kremer_whangbo_2022, title={High-Spin Orbital Interactions Across van der Waals Gaps Controlling the Interlayer Ferromagnetism in van der Waals Ferromagnets}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.2c06741}, abstractNote={We examined what interactions control the sign and strength of the interlayer coupling in van der Waals ferromagnets such as Fe3-xGeTe2, Cr2Ge2Te6, CrI3, and VI3 to find that high-spin orbital interactions across the van der Waals gaps are a key to understanding their ferromagnetism. Interlayer ferromagnetic coupling in Fe3-xGeTe2, Cr2Ge2Te6, and CrI3 is governed by the high-spin two-orbital two-electron destabilization, but that in VI3 by the high-spin four-orbital two-electron stabilization. These interactions explain a number of seemingly puzzling observations in van der Waals ferromagnets.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Koo, Hyun-Joo and Kremer, Reinhard K. and Whangbo, Myung-Hwan}, year={2022}, month={Aug} }
 @article{moskin_kozlyakova_shvanskaya_chareev_koo_whangbo_vasiliev_2022, title={Highly anisotropic 1/3-magnetization plateau in a ferrimagnet Cs2Cu3(SeO3)(4)center dot 2H(2)O: topology of magnetic bonding necessary for magnetization plateau}, volume={52}, ISSN={["1477-9234"]}, DOI={10.1039/d2dt03517k}, abstractNote={We prepared Cs2Cu3(SeO3)4·2H2O composed of Cu2+ ions at square-planar coordination sites and characterized its structural and magnetic properties, to show that Cs2Cu3(SeO3)4·2H2O is a ferrimagnet exhibiting a highly anisotropic 1/3-magnetization plateau. This unprecedented anisotropy in a magnetization plateau is the consequence of three effects, namely, the orthogonal arrangements of the corner-sharing CuO4 square planes, the nearest-neighbour antiferromagnetic exchange, and the anisotropic g-factor of the Cu2+ ions at square-planar coordination sites. By analyzing the topology of magnetic bonding, we found why magnetic plateaus are observed only for certain ferrimagnets and antiferromagnets.}, number={1}, journal={DALTON TRANSACTIONS}, author={Moskin, A. V. and Kozlyakova, E. S. and Shvanskaya, L. V. and Chareev, D. A. and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Vasiliev, A. N.}, year={2022}, month={Dec}, pages={118–127} }
 @article{vasilchikova_vasiliev_evstigneeva_nalbandyan_lee_koo_whangbo_2022, title={Magnetic Properties of A(2)Ni(2)TeO(6) (A = K, Li): Zigzag Order in the Honeycomb Layers of Ni2+ Ions Induced by First and Third Nearest-Neighbor Spin Exchanges}, volume={15}, ISSN={["1996-1944"]}, DOI={10.3390/ma15072563}, abstractNote={The static and dynamic magnetic properties and the specific heat of K2Ni2TeO6 and Li2Ni2TeO6 were examined and it was found that they undergo a long-range ordering at TN = 22.8 and 24.4 K, respectively, but exhibit a strong short-range order. At high temperature, the magnetic susceptibilities of K2Ni2TeO6 and Li2Ni2TeO6 are described by a Curie-Weiss law, with Curie-Weiss temperatures Θ of approximately -13 and -20 K, respectively, leading to the effective magnetic moment of about 4.46 ± 0.01 μB per formula unit, as expected for Ni2+ (S = 1) ions. In the paramagnetic region, the ESR spectra of K2Ni2TeO6 and Li2Ni2TeO6 show a single Lorentzian-shaped line characterized by the isotropic effective g-factor, g = 2.19 ± 0.01. The energy-mapping analysis shows that the honeycomb layers of A2Ni2TeO6 (A = K, Li) and Li3Ni2SbO6 adopt a zigzag order, in which zigzag ferromagnetic chains are antiferromagnetically coupled, because the third nearest-neighbor spin exchanges are strongly antiferromagnetic while the first nearest-neighbor spin exchanges are strongly ferromagnetic, and that adjacent zigzag-ordered honeycomb layers prefer to be ferromagnetically coupled. The short-range order of the zigzag-ordered honeycomb lattices of K2Ni2TeO6 and Li2Ni2TeO6 is equivalent to that of an antiferromagnetic uniform chain, and is related to the short-range order of the ferromagnetic chains along the direction perpendicular to the chains.}, number={7}, journal={MATERIALS}, author={Vasilchikova, Tatyana and Vasiliev, Alexander and Evstigneeva, Maria and Nalbandyan, Vladimir and Lee, Ji-Sun and Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2022}, month={Apr} }
 @misc{jiang_deng_whangbo_guo_2022, title={Material research from the viewpoint of functional motifs}, volume={9}, ISSN={["2053-714X"]}, DOI={10.1093/nsr/nwac017}, abstractNote={Abstract As early as 2001, the need for the ‘functional motif theory’ was pointed out, to assist the rational design of functional materials. The properties of materials are determined by their functional motifs and how they are arranged in the materials. Uncovering functional motifs and their arrangements is crucial in understanding the properties of materials and rationally designing new materials of desired properties. The functional motifs of materials are the critical microstructural units (e.g. constituent components and building blocks) that play a decisive role in generating certain material functions, and can not be replaced with other structural units without the loss, or significant suppression, of relevant functions. The role of functional motifs and their arrangement in materials, with representative examples, is presented. The microscopic structures of these examples can be classified into six types on a length scale smaller than ∼10 nm with maximum subatomic resolution, i.e. crystal, magnetic, aperiodic, defect, local and electronic structures. Functional motif analysis can be employed in the function-oriented design of materials, as elucidated by taking infrared non-linear optical materials as an example. Machine learning is more efficient in predicting material properties and screening materials with high efficiency than high-throughput experimentation and high-throughput calculations. In order to extract functional motifs and find their quantitative relationships, the development of sufficiently reliable databases for material structures and properties is imperative.}, number={7}, journal={NATIONAL SCIENCE REVIEW}, author={Jiang, Xiao-Ming and Deng, Shuiquan and Whangbo, Myung-Hwan and Guo, Guo-Cong}, year={2022}, month={Aug} }
 @article{xu_huang_cheng_whangbo_deng_2022, title={Microscopic Mechanism of the Heat-Induced Blueshift in Phosphors and a Logarithmic Energy Dependence on the Nearest Dopant-Vacancy Distance}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202116404}, abstractNote={Heat-induced blueshift (HIB) observed in many luminescent materials is a puzzling phenomenon that has remained unexplained for decades. By using the high-throughput first-principles calculations and energy-screening techniques, we generated a number of model structures for five phosphors, RbLi[Li3 SiO4 ]2 :Eu2+ , Na[Li3 SiO4 ]:Eu2+ , K[Li3 SiO4 ]:Eu2+ , Sr[LiAl3 N4 ]:Eu2+ , and Ca[LiAl3 N4 ]:Eu2+ . Our analyses suggest, to a first approximation, a logarithmic energy dependence on the nearest distance between the dopant and the metal-cation vacancy. By identifying the 5d→4f transition energies from the electronic structures calculated for the screened model structures, we show that the vibration of the Eu2+ ion lying in an asymmetric and anharmonic potential well couples with the electronic states, leading to their HIB phenomena.}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Xu, Jing and Huang, Xueli and Cheng, Xiyue and Whangbo, Myung-Hwan and Deng, Shuiquan}, year={2022}, month={Feb} }
 @article{kremer_bette_bruecher_nuss_schulz_whangbo_koo_2022, title={Multiple strongly coupled antiferromagnetic spin S=1/2 dimers in liroconite Cu2Al(As,P)O-4(OH)(4)center dot 4H(2)O}, ISSN={["2196-7105"]}, DOI={10.1515/zkri-2022-0040}, abstractNote={Abstract We report on the magneto-structural properties of the rare copper aluminum hydroxo-arsenate mineral liroconite with chemical composition Cu 2 AlAs 1− x P x O 4 (OH) 4 ·4H 2 O ( x ≈ 0.2). In order to characterize the natural mineral sample chemical analyses, X-ray single crystal and powder diffraction, heat capacity and crystal water desorption, anisotropic thermal expansion and Raman scattering and magnetic susceptibility investigations have been carried out. The magnetic properties are well described by two discrete oxygen bridged Cu 2+ spin S = 1/2 dimers with antiferromagnetic spin exchange ranging between −320 K and −136 K, depending on to which group-15 five-valent cation, As 5+ or P 5+ , the dimer bridging oxygen atoms coordinate to. Accordingly the temperature dependence of the magnetic susceptibilities can be well fitted to a sum of two Bleaney–Bowers type spin S = 1/2 dimer susceptibilities suggesting that the dimers show negligible mixed coordination to (AsO 4 ) 3− /(PO 4 ) 3− tetrahedra. DFT + U calculation confirm the ratio of the spin exchange parameters of the (AsO 4 ) 3− or (PO 4 ) 3− coordinated Cu 2+ – Cu 2+ dimers. Inter dimer spin exchange is about two orders of magnitude smaller than intra dimer exchange.}, journal={ZEITSCHRIFT FUR KRISTALLOGRAPHIE-CRYSTALLINE MATERIALS}, author={Kremer, Reinhard K. and Bette, Sebastian and Bruecher, Eva and Nuss, Juergen and Schulz, Armin and Whangbo, Myung-Hwan and Koo, Hyun-Joo}, year={2022}, month={Sep} }
 @article{almoussawi_yao_guo_whangbo_dupray_clevers_deng_kabbour_2022, title={Negative Second Harmonic Response of Sn(4+)in the Fresnoite Oxysulfide Ba2SnSSi2O7}, volume={34}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.1c04296}, abstractNote={Oxychalcogenides are promising candidates for the design of IR nonlinear optical materials. Here, we prepared the first oxysulfide in the polar Fresnoite mineral type, Ba2SnSSi2O7, and show that it has rare tin square pyramids, SnO4S, with apical Sn–S bond. These units and the Si2O7 groups are corner-shared to form the SnSSi2O7 layer with their Sn–S and apical Si–O bonds pointed along the polar c axis. Second harmonic generation measurements reveal that Ba2SnSSi2O7 is an IR nonlinear optical (NLO) compound. Formally, Ba2SnSSi2O7 results from the mineral Fresnoite, Ba2TiOSi2O7, by replacing the TiO5 square pyramid with the SnO4S square pyramid. This substitution increases the apical/the equatorial bond ratio of the square pyramid, namely, Ti–Oap/Ti–Oeq = 1.66/2.00 = 0.83 in TiO5, and Sn–S/Sn–O = 2.03/2.31 = 0.88 in SnO4S. This change has a major impact on the cleavage along the stacking polar c axis and on the second harmonic generation response, which decreases from Ba2TiOSi2O7 to Ba2SnSSi2O7 by a factor greater than 2. The atom response theory analyses based on the density functional theory calculations reveal a remarkable difference between Ba2TiOSi2O7 and Ba2SnSSi2O7; the second harmonic generation is positive for the Ti4+ ion of Ba2TiOSi2O7 but negative for the Sn4+ ion of Ba2SnSSi2O7. A Tauc plot analysis for Ba2SnSSi2O7 assuming indirect and direct transitions led to the optical band gaps of 2.4 and 2.7 eV, respectively.}, number={10}, journal={CHEMISTRY OF MATERIALS}, author={Almoussawi, Batoul and Yao, Wen-Dong and Guo, Sheng-Ping and Whangbo, Myung-Hwan and Dupray, Valerie and Clevers, Simon and Deng, Shuiquan and Kabbour, Houria}, year={2022}, month={May}, pages={4375–4383} }
 @article{vasiliev_berdonosov_kozlyakova_maximova_murtazoev_dolgikh_lyssenko_pchelkina_gorbunov_chung_et al._2022, title={Observation of a 1/3 magnetization plateau in Pb2Cu10O4(SeO3)(4)Cl-7 arising from (Cu2+)(7) clusters of corner-sharing (Cu2+)(4) tetrahedra}, ISSN={["1477-9234"]}, DOI={10.1039/d2dt02316d}, abstractNote={A mixed-valence compound Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 has a complex structure consisting of one nonmagnetic Cu + ( S = 0) ion and four nonequivalent magnetic Cu 2+ ( S = 1/2) ions.}, journal={DALTON TRANSACTIONS}, author={Vasiliev, A. N. and Berdonosov, P. S. and Kozlyakova, E. S. and Maximova, O. and Murtazoev, A. F. and Dolgikh, V. A. and Lyssenko, K. A. and Pchelkina, Z. and Gorbunov, D. and Chung, S. H. and et al.}, year={2022}, month={Sep} }
 @article{amano patino_denis romero_koo_avdeev_injac_goto_whangbo_shimakawa_2022, title={Orthogonal antiferromagnetism to canted ferromagnetism in CaCo3Ti4O12 quadruple perovskite driven by underlying kagome lattices}, volume={3}, ISSN={["2662-4443"]}, DOI={10.1038/s43246-022-00274-y}, abstractNote={Abstract AA ′ 3 B 4 O 12 quadruple perovskites, with magnetic A ′ and non-magnetic B cations, are characterized by a wide range of complex magnetic structures. These are due to a variety of competing spin-exchange interactions up to the fourth nearest neighbours. Here, we synthesize and characterize the magnetic behaviour of the CaCo 3 Ti 4 O 12 quadruple perovskite. We find that in the absence of an external magnetic field, the system undergoes antiferromagnetic ordering at 9.3 K. This magnetic structure consists of three interpenetrating mutually orthogonal magnetic sublattices. Under an applied magnetic field, this antiferromagnetic structure evolves into a canted ferromagnetic structure. In explaining these magnetic structures, as well as the seemingly unrelated magnetic structures found in other quadruple perovskites, we suggest a crucial role played by the underlying kagome lattices in these systems. All observed magnetic structures of these materials represent indeed one of the three possible ways to reduce spin frustration in the A ′ site kagome layers. More specifically, our survey of the magnetic structures observed for quadruple perovskites AA ′ 3 B 4 O 12 reveals the following three ways to reduce spin frustration, namely to make each layer ferromagnetic, to adopt a compromise 120° spin arrangement in each layer, or to have a magnetic structure with a vanishing sum of all second nearest-neighbour spin exchanges.}, number={1}, journal={COMMUNICATIONS MATERIALS}, author={Amano Patino, Midori and Denis Romero, Fabio and Koo, Hyun-Joo and Avdeev, Maxim and Injac, Sean D. A. and Goto, Masato and Whangbo, Myung-Hwan and Shimakawa, Yuichi}, year={2022}, month={Aug} }
 @article{yang_huang_cheng_maggard_whangbo_luan_deng_2022, title={Prediction of Large Second Harmonic Generation in the Metal-Oxide/Organic Hybrid Compound CuMoO3(p2c)}, volume={14}, ISSN={["2073-8994"]}, url={https://www.mdpi.com/2073-8994/14/4/824}, DOI={10.3390/sym14040824}, abstractNote={Noncentrosymmetric hybrid framework (HF) materials are an important system in discovering new practical second-order nonlinear optical materials. We calculated the second harmonic generation (SHG) response of a noncentrosymmetric (NCS) organic–inorganic HF compound, CuMoO3(p2c) (p2c = pyrazine-2-carboxylate) to find that it exhibits the largest SHG response among all known NCS HF materials with one-dimensional helical chains. Further atom response theory analysis revealed that the metal atoms Cu and Mo contribute much more strongly than do nonmetal atoms in determining the strength of the SHG response, which is a novel example in nonlinear optical materials known to date.}, number={4}, journal={SYMMETRY-BASEL}, author={Yang, Tingting and Huang, Xueli and Cheng, Xiyue and Maggard, Paul A. and Whangbo, Myung-Hwan and Luan, Chengkai and Deng, Shuiquan}, year={2022}, month={Apr} }
 @article{markina_vasilchikova_kuznetsova_berdonosov_olenev_chung_koo_whangbo_vasiliev_2022, title={Preparation and Characterization of Francisite Solid Solutions Cu3Bi(S(e1-x)TexO(3))(2)O2Br (x=0-1): Possibility for Francisites as Starting Materials for Oxide van der Waals Ferromagnets}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.2c02865}, abstractNote={We synthesized the solid solutions Cu3Bi(Se1–xTexO3)2O2Br (x = 0, 0.25, 0.5, 0.75, 1) for the first time and characterized their structures by X-ray diffraction (XRD) measurements and their magnetic properties by electron spin resonance (ESR), magnetic susceptibility, magnetization, and specific heat measurements as well as by density functional theory (DFT) calculations. The Néel temperature TN and the critical field μ0HC needed for the metamagnetic transition increase with x, while the magnetization at a given magnetic field and the Curie–Weiss temperature Θ decrease with x. We show that the tendency for the interlayer antiferromagnetic (AFM) coupling in francisites is not explained by interlayer spin exchange but by the interlayer high-spin orbital interaction that occur across the van der Waals (vdW) gaps, hence indicating that francisites are vdW ferromagnets. This is surprising because, so far, well-established vdW ferromagnets are either layered tellurides or layered iodides. The trends in TN, μ0HC, and the magnetization of Cu3Bi(Se1–xTexO3)2O2Br as a function of x are well explained by the interlayer AFM interactions, and that in the Θ is explained by the intralayer spin exchanges. We proposed how one might modify francisites to make their interlayer interactions ferromagnetic (FM), hence leading to oxide vdW ferromagnets.}, journal={CHEMISTRY OF MATERIALS}, author={Markina, Maria and Vasilchikova, Tatyana and Kuznetsova, Elena and Berdonosov, Peter and Olenev, Andrey and Chung, Seung Hwan and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Vasiliev, Alexander}, year={2022}, month={Dec} }
 @article{lee_park_shim_whangbo_2022, title={Skin-Deep Aspect of Thermopower in Bi(2)Q(3), PbQ, and BiCuQO (Q = Se, Te): Hidden One-Dimensional Character of Their Band Edges Leading to High Thermopower}, ISSN={["1520-4898"]}, DOI={10.1021/acs.accounts.2c00255}, abstractNote={ConspectusThermoelectric (TE) materials have received much attention because of their ability to convert heat energy to electrical energy. At a given temperature T, the efficiency of a TE material for this energy conversion is measured by the figure of merit zT, which is related to the thermopower (or Seebeck coefficient) S, the thermal conductivity κ, and the electrical conductivity σ of the TE material as zT = (S2σT)/κ. Bi2Q3 and PbQ (Q = Se, Te) are efficient TE materials with high zT, although they are not ecofriendly and their stability is poor at high temperature. In principle, a TE material can have a high zT if it has a low thermal conductivity and a high electrical conductivity, but the latter condition is hardly met in a real material because the parameters S, σ and κ have a conflicting dependence on material properties. The difficulty in searching for TE materials of high zT is even more exasperated because the relationship between the thermopower S and the carrier density n (hereafter, the S-vs-n relationship) for the well-known hole-doped samples of BiCuSeO showed that the hole carriers responsible for their thermopower are associated largely with the electronic states lying within ∼0.5 eV of its valence band maximum (VBM). Thus, the states governing the TE properties lie in the "skin-deep" region from the VBM. For electron-doped TE systems, the electron carriers responsible for their thermopower should also be associated with the electronic states lying within ∼0.5 eV of the conduction band minimum (CBM). This makes it difficult to predict TE materials of high zT. One faces a similar skin-deep phenomenon in searching for superconductors of high transition temperature because the transition from a normal metallic to a superconducting state involves the normal metallic states in the vicinity of the Fermi level EF. Other skin-deep phenomena in metallic compounds include the formation of charge density wave (CDW), which involves the electronic states in the vicinity of their Fermi levels. For magnetic materials of transition-metal ions, the preferred orientation of their spin moments is a skin-deep phenomenon because it is governed by the interaction between the highest-occupied and the lowest unoccupied d-states of these ions. In the present work we probe the issues concerning how to find the possible range of thermopower expected for a given TE material and hence how to recognize what experimental values of thermopower are expected or unusual. For these purposes, we analyze the accumulated S and n data on the three well-studied TE materials, Bi2Q3, PbQ, and BiCuQO (Q = Se, Te), as representative examples, in terms of the ideal theoretical S-vs-n relationships, which we determine for their defect-free Bi2Q3, PbQ, and BiCuQO structures using density functional theory (DFT) calculations under the rigid band approximation. We find that the general trends in the experimental S-vs-n relationships are reasonably well explained by the calculated S-vs-n relationships, and the carrier densities covering these relationships are associated with the states lying within ∼0.5 eV from their band edges confirming the skin-deep nature of their thermoelectric properties. Despite the fact that these TE materials are not one-dimensional (1D) in structure, they mostly possess sharp density-of-state peaks around their band edges because their band dispersions have a hidden 1D character so their thermopower is generally high in magnitude.}, journal={ACCOUNTS OF CHEMICAL RESEARCH}, author={Lee, Changhoon and Park, Taesu and Shim, Ji Hoon and Whangbo, Myung-Hwan}, year={2022}, month={Sep} }
 @article{whangbo_kremer_koo_2022, title={Unusually High Magnetic Moments Reported for the High-Spin Co2+ Ions at Axially Elongated CoO4X2 (X = Cl, Br, S, Se) Octahedral Sites: Overestimated Magnetic Moments Caused by Underestimated Magnetic Form Factors}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.2c05586}, abstractNote={An irreconcilable discrepancy between theory and experiment concerning the magnetic moments of the high-spin Co2+ (d7, S = 3/2) ions at the axially elongated CoO4X2 (X = Cl, Br, S, Se) octahedral sites was pointed out in our recent study [ Inorg. Chem. 2020, 59, 18319−18324]. The magnetic moments μobs of the Co2+ ions in materials containing the CoO4X2 units, determined from refinements of powder neutron diffraction patterns collected in their magnetically ordered states, were found to be notably larger than the spin-only moment of 3 μB (namely, 3.22–4.45 μB). Characteristically, the moments increase almost linearly with the bond-length ratio R = rCo–X/rCo–O, despite the fact that the orbital moments of the Co2+ ions are essentially quenched according to theoretical analyses and DFT + U + SOC computations. In this work, we probe the probable cause for the overestimation of magnetic moments in the ordered magnetic structures. We argue that the overestimated magnetic moments of the Co2+ ions and their increase with the bond-length ratio R originate from the underestimated magnetic form factors of the Co2+ ions at the CoO4X2 octahedral sites. The magnetic form factor F(q) of the Co2+ ion in each CoO4X2 octahedron is the Fourier transform of the magnetic moment distribution ρ(r) around the Co2+ ion, which is the electron density distribution associated with the magnetic orbitals (i.e., the singly occupied d-states) of the CoO4X2 octahedron. The conventional implementation of the magnetic form factor in refinement codes employed an approximation with a q-dependence calculated from the atomic wave function of the isolated ion. Since the spin moment distribution of ρ(r) at the axially elongated CoO4X2 (X = Cl, Br, S, Se) octahedral sites is delocalized from the Co2+ sites to its surrounding ligands, the moment distribution becomes anisotropic in shape. Use of the truncated and spherical approximation underestimates the form factor of the Co2+ ion, and its use in neutron diffraction refinements overestimates the magnetic moments. This effect becomes more pronounced as the moment density distribution is more delocalized along the Co–X direction.}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Whangbo, Myung-Hwan and Kremer, Reinhard K. and Koo, Hyun-Joo}, year={2022}, month={Sep} }
 @article{luo_xu_xia_pang_xu_whangbo_sun_chen_2021, title={Anomaly Negative Resistance Phenomena in Highly Epitaxial PrBa0.7Ca0.3Co2O5+delta Thin Films Induced from Superfast Redox Reactions}, volume={11}, ISSN={["2073-4344"]}, DOI={10.3390/catal11121441}, abstractNote={Thin films of Ca-doped double perovskite, PrBa0.7Ca0.3Co2O5+δ (PBCC), were epitaxially grown on (001) SrTiO3, and their redox reactions under a switching flow of H2 and O2 gases were examined at various temperatures by measuring the resistance R(t) of the films as a function of the gas flow time t. In the temperature range between 350 and 725 °C, these thin films are reduced and oxidized in an ultrafast manner under the flow of H2 and O2 gases, respectively, suggesting that PBCC thin films are promising candidates for developing ultra-sensitive oxygen sensors or SOFC cathodes at intermediate or high temperatures. When the gas flow is switched to O2, the reduced PBCC thin films exhibit a negative resistance at temperatures above 600 °C but a positive resistance at temperatures below 600 °C. The probable cause for these anomalous transport properties is the diffusion of the H atoms from the cathode to the anode in the PBCC film, which provides a current opposite to that resulting from the external voltage.}, number={12}, journal={CATALYSTS}, author={Luo, Yumei and Xu, Xing and Xia, Yudong and Pang, Shengli and Xu, Fen and Whangbo, Myung-Hwan and Sun, Lixian and Chen, Chonglin}, year={2021}, month={Dec} }
 @article{xing_zhou_liu_wang_wang_zheng_dai_whangbo_huang_2021, title={Atomically dispersed cobalt-based species anchored on polythiophene as an efficient electrocatalyst for oxygen evolution reaction}, volume={545}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2021.148943}, abstractNote={For clean and renewable energy conversion systems, it is important to develop efficient, earth-abundant, low-cost and stable electrocatalysts for oxygen evolution reaction (OER). Herein, we prepared an atomically dispersed cobalt coordinated with oxygen and sulfur species on the conductive polymer polythiophene (PTh) via CoS bond as a stable noble-metal-free electrocatalyst for the OER. A novel cobalt-based catalytic site structure, CoxOyS4, is successfully fabricated. The resulting electrocatalyst, [email protected], exhibits an excellent OER performance with overpotential of 338 mV versus reversible hydrogen electrode (RHE) at a current density of 10 mA cm−2 and the Tafel slope of 52 mV dec−1 in alkaline electrolyte. This performance is better than that of the commercial RuO2 and even comparable with the state-of-the-art catalyst IrO2. Our work suggests that the atomically dispersed cobalt-based species decorated PTh may be a good alternative for precious-metal-based catalysts.}, journal={APPLIED SURFACE SCIENCE}, author={Xing, Danning and Zhou, Peng and Liu, Yuanyuan and Wang, Zeyan and Wang, Peng and Zheng, Zhaoke and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2021}, month={Apr} }
 @article{zhao_liu_hu_jia_cui_wu_whangbo_ren_2021, title={Difference in magnetic anisotropy of the ferromagnetic monolayers VI3 and CrI3}, volume={103}, ISSN={["2469-9969"]}, DOI={10.1103/PhysRevB.103.014438}, abstractNote={Concerning the magnetic anisotropy and magnetic moments of the ${M}^{3+}$ $(M=\mathrm{V}, \mathrm{Cr})$ ions in ferromagnetic $(\mathrm{FM}){M\mathrm{I}}_{3}$ monolayers, which have a honeycomb pattern of edge-sharing ${M\mathrm{I}}_{6}$ octahedra, conflicting observations have been reported in experimental and theoretical studies. We resolve these conflicts by determining the magnetic anisotropy energies for the ${M}^{3+}$ ions of ${M\mathrm{I}}_{3}$ monolayers, by analyzing their preferred spin orientations in terms of the selection rules based on the highest occupied molecular orbital--lowest unoccupied molecular orbital interactions of the ${M\mathrm{I}}_{6}$ octahedra, and by discussing whether or not the ${M}^{3+}$ ions are uniaxial. Here we show that the FM monolayer ${\mathrm{VI}}_{3}$ is uniaxial, but that of ${\mathrm{CrI}}_{3}$ is not. The magnetic anisotropy energy for the ${\mathrm{V}}^{3+}({d}^{2},S=1)$ ion of ${\mathrm{VI}}_{3}$ is greater than that for the ${\mathrm{Cr}}^{3+}$ $({d}^{3},$ $S=3/2)$ ion of ${\mathrm{CrI}}_{3}$ by more than an order of magnitude (i.e., \ensuremath{\sim}8 vs \ensuremath{\sim}0.6 meV). The ${\mathrm{V}}^{3+}$ ion exhibits uniaxial magnetism because its orbital quantum number L is not zero $(L=\phantom{\rule{0.16em}{0ex}}1)$, in contrast to the ${\mathrm{Cr}}^{3+}$ ion $(L=0)$.}, number={1}, journal={PHYSICAL REVIEW B}, author={Zhao, Guo-Dong and Liu, Xingen and Hu, Tao and Jia, Fanhao and Cui, Yaning and Wu, Wei and Whangbo, Myung-Hwan and Ren, Wei}, year={2021}, month={Jan} }
 @article{luo_xu_cheng_li_huang_whangbo_deng_hong_2021, title={High partial thermal conductivity of luminescence sites: a crucial factor for reducing the heat-induced lowering of the luminescence efficiency}, ISSN={["2050-7534"]}, DOI={10.1039/d1tc02287c}, abstractNote={The high partial thermal conductivity of luminescence sites is associated with the reduction of the heat-induced lowering of the luminescence efficiency of phosphors. This finding may be helpful for screening efficient phosphors.}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Luo, Ni and Xu, Jing and Cheng, Xiyue and Li, ZhenHua and Huang, Yidong and Whangbo, Myung-Hwan and Deng, Shuiquan and Hong, Maochun}, year={2021}, month={Sep} }
 @article{etourneau_delmas_jobic_whangbo_2021, title={In Honor of John Bannister Goodenough, an Outstanding Visionary}, volume={26}, ISSN={["1420-3049"]}, DOI={10.3390/molecules26216624}, abstractNote={John B [...]}, number={21}, journal={MOLECULES}, author={Etourneau, Jean and Delmas, Claude and Jobic, Stephane and Whangbo, Myung-Hwan}, year={2021}, month={Nov} }
 @misc{whangbo_koo_kremer_2021, title={Spin Exchanges between Transition Metal Ions Governed by the Ligand p-Orbitals in Their Magnetic Orbitals}, volume={26}, ISSN={["1420-3049"]}, DOI={10.3390/molecules26030531}, abstractNote={In this review on spin exchanges, written to provide guidelines useful for finding the spin lattice relevant for any given magnetic solid, we discuss how the values of spin exchanges in transition metal magnetic compounds are quantitatively determined from electronic structure calculations, which electronic factors control whether a spin exchange is antiferromagnetic or ferromagnetic, and how these factors are related to the geometrical parameters of the spin exchange path. In an extended solid containing transition metal magnetic ions, each metal ion M is surrounded with main-group ligands L to form an MLn polyhedron (typically, n = 3–6), and the unpaired spins of M are represented by the singly-occupied d-states (i.e., the magnetic orbitals) of MLn. Each magnetic orbital has the metal d-orbital combined out-of-phase with the ligand p-orbitals; therefore, the spin exchanges between adjacent metal ions M lead not only to the M–L–M-type exchanges, but also to the M–L…L–M-type exchanges in which the two metal ions do not share a common ligand. The latter can be further modified by d0 cations A such as V5+ and W6+ to bridge the L…L contact generating M–L…A…L–M-type exchanges. We describe several qualitative rules for predicting whether the M–L…L–M and M–L…A…L–M-type exchanges are antiferromagnetic or ferromagnetic by analyzing how the ligand p-orbitals in their magnetic orbitals (the ligand p-orbital tails, for short) are arranged in the exchange paths. Finally, we illustrate how these rules work by analyzing the crystal structures and magnetic properties of four cuprates of current interest: α-CuV2O6, LiCuVO4, (CuCl)LaNb2O7, and Cu3(CO3)2(OH)2.}, number={3}, journal={MOLECULES}, author={Whangbo, Myung-Hwan and Koo, Hyun-Joo and Kremer, Reinhard K.}, year={2021}, month={Feb} }
 @misc{li_yu_lou_feng_whangbo_xiang_2021, title={Spin Hamiltonians in Magnets: Theories and Computations}, volume={26}, ISSN={["1420-3049"]}, DOI={10.3390/molecules26040803}, abstractNote={The effective spin Hamiltonian method has drawn considerable attention for its power to explain and predict magnetic properties in various intriguing materials. In this review, we summarize different types of interactions between spins (hereafter, spin interactions, for short) that may be used in effective spin Hamiltonians as well as the various methods of computing the interaction parameters. A detailed discussion about the merits and possible pitfalls of each technique of computing interaction parameters is provided.}, number={4}, journal={MOLECULES}, author={Li, Xueyang and Yu, Hongyu and Lou, Feng and Feng, Junsheng and Whangbo, Myung-Hwan and Xiang, Hongjun}, year={2021}, month={Feb} }
 @article{koo_kremer_whangbo_2021, title={Unusual Spin Exchanges Mediated by the Molecular Anion P2S64-: Theoretical Analyses of the Magnetic Ground States, Magnetic Anisotropy and Spin Exchanges of MPS3 (M = Mn, Fe, Co, Ni)}, volume={26}, ISSN={["1420-3049"]}, DOI={10.3390/molecules26051410}, abstractNote={We examined the magnetic ground states, the preferred spin orientations and the spin exchanges of four layered phases MPS3 (M = Mn, Fe, Co, Ni) by first principles density functional theory plus onsite repulsion (DFT + U) calculations. The magnetic ground states predicted for MPS3 by DFT + U calculations using their optimized crystal structures are in agreement with experiment for M = Mn, Co and Ni, but not for FePS3. DFT + U calculations including spin-orbit coupling correctly predict the observed spin orientations for FePS3, CoPS3 and NiPS3, but not for MnPS3. Further analyses suggest that the ||z spin direction observed for the Mn2+ ions of MnPS3 is caused by the magnetic dipole–dipole interaction in its magnetic ground state. Noting that the spin exchanges are determined by the ligand p-orbital tails of magnetic orbitals, we formulated qualitative rules governing spin exchanges as the guidelines for discussing and estimating the spin exchanges of magnetic solids. Use of these rules allowed us to recognize several unusual exchanges of MPS3, which are mediated by the symmetry-adapted group orbitals of P2S64− and exhibit unusual features unknown from other types of spin exchanges.}, number={5}, journal={MOLECULES}, author={Koo, Hyun-Joo and Kremer, Reinhard and Whangbo, Myung-Hwan}, year={2021}, month={Mar} }
 @article{myung-hwan_mao-chun_shui-quan_2020, title={Atom Response Theory of Nonlinear Optical Responses and Its Applications}, volume={39}, ISSN={["0254-5861"]}, DOI={10.14102/j.cnki.0254-5861.2011-3019}, number={12}, journal={CHINESE JOURNAL OF STRUCTURAL CHEMISTRY}, author={Myung-Hwan, Whangbo and Mao-Chun, Hong and Shui-Quan, Deng}, year={2020}, month={Dec}, pages={2172–2181} }
 @article{gao_wu_liang_wang_zheng_wang_liu_dai_whangbo_huang_2020, title={Cu2O Nanoparticles with Both {100} and {111} Facets for Enhancing the Selectivity and Activity of CO2 Electroreduction to Ethylene}, volume={7}, ISSN={["2198-3844"]}, DOI={10.1002/advs.201902820}, abstractNote={Cu2O nanoparticles (NPs) enclosed with different crystal facets, namely, c-Cu2O NPs with {100} facets, o-Cu2O NPs with {111} facets, and t-Cu2O NPs with both {111} and {100} facets, are prepared and their electrocatalytic properties for the reduction of CO2 to C2H4 are evaluated. It is shown that the selectivity and activity of the C2H4 production depend strongly on the crystal facets exposed in Cu2O NPs. The selectivities for the C2H4 production increases in the order, c-Cu2O < o-Cu2O < t-Cu2O, (with FEC2H4 = 38%, 45%, and 59%, respectively). This study suggests that Cu2O NPs are more likely responsible for the selectivity and activity for the C2H4 production than the metallic Cu NPs produced on the surface of Cu2O NPs. This work provides a new route for enhancing the selectivity of the electrocatalytic CO2 reduction by crystal facet engineering.}, number={6}, journal={ADVANCED SCIENCE}, author={Gao, Yugang and Wu, Qian and Liang, Xizhuang and Wang, Zeyan and Zheng, Zhaoke and Wang, Peng and Liu, Yuanyuan and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2020}, month={Mar} }
 @article{wang_wang_zhang_jiang_bao_cheng_zheng_wang_liu_whangbo_et al._2020, title={Enhancing the Photoelectrochemical Water Oxidation Reaction of BiVO4 Photoanode by Employing Carbon Spheres as Electron Reservoirs}, volume={10}, ISSN={["2155-5435"]}, DOI={10.1021/acscatal.0c03671}, abstractNote={The rate-determining step of the photoelectrochemical (PEC) water splitting is the water oxidation reaction at the photoanode, which is 4 orders of magnitude slower than the water reduction reactio...}, number={21}, journal={ACS CATALYSIS}, author={Wang, Minrui and Wang, Zeyan and Zhang, Bo and Jiang, Weiyi and Bao, Xiaolei and Cheng, Hefeng and Zheng, Zhaoke and Wang, Peng and Liu, Yuanyuan and Whangbo, Myung-Hwan and et al.}, year={2020}, month={Nov}, pages={13031–13039} }
 @article{wang_mao_niu_shen_whangbo_huang_dai_2020, title={Ferromagnetic dual topological insulator in a two-dimensional honeycomb lattice}, volume={7}, ISSN={["2051-6355"]}, DOI={10.1039/d0mh00803f}, abstractNote={Magnetic topological insulators (TIs), including the quantum anomalous Hall effect and antiferromagnetic TIs, have attracted significant attention owing to the exotic properties they give rise to, however, ferromagnetic TIs with gapless surface/edge states and a nonzero topological invariant have not been reported so far.}, number={9}, journal={MATERIALS HORIZONS}, author={Wang, Hao and Mao, Ning and Niu, Chengwang and Shen, Shiying and Whangbo, Myung-Hwan and Huang, Baibiao and Dai, Ying}, year={2020}, month={Sep}, pages={2431–2438} }
 @article{zvereva_raganyan_vasilchikova_nalbandyan_gafurov_vavilova_zakharov_koo_pomjakushin_susloparova_et al._2020, title={Hidden magnetic order in the triangular-lattice magnet Li2MnTeO6}, volume={102}, ISSN={["2469-9969"]}, DOI={10.1103/PhysRevB.102.094433}, abstractNote={The manganese tellurate Li2MnTeO6 consists of trigonal spin lattices made up of Mn4+ (d3, S = 3/2) ions. The magnetic properties of this compound were characterized by several experimental techniques, which include magnetic susceptibility, specific heat, dielectric permittivity, electron spin resonance (ESR), nuclear magnetic resonance (NMR) and neutron powder diffraction (NPD) measurements, and by density functional calculations (DFT). The magnetic susceptibility chi(T) demonstrates very unusual behavior. It isdescribed by the Curie-Weiss law at high temperature with Curie-Weiss temperature of Theta = -74 K, exhibits no obvious anomaly indicative of a long-range magnetic ordering at low magnetic fields. At high magnetic fields, however, the character of chi(T) changes showing a maximum at about 9 K. That this maximum of chi(T) reflects the onset of an antiferromagnetic order was confirmed by specific heat measurements, which exhibit a clear lambda-type anomaly at TN around 8.5 K even at zero magnetic field, and by 7Li NMR and dielectric permittivity measurements. The magnetic structure of Li2MnTeO6, determined by neutron powder diffraction measurements at 1.6 K, is described by the 120-degree non-collinear spin structure with the propagation vector k = (1/3, 1/3, 0). Consistent with this finding, the spin exchange interactions evaluated for Li2MnTeO6 by density functional calculations are dominated by the nearest-neighbor antiferromagnetic exchange within each triangular spin lattice. This spin lattice is strongly spin frustrated with f = |Theta|/TN around 8 and exhibits a two-dimensional magnetic character in a broad temperature range above TN.}, number={9}, journal={PHYSICAL REVIEW B}, author={Zvereva, E. A. and Raganyan, G. and Vasilchikova, T. M. and Nalbandyan, V. B. and Gafurov, D. A. and Vavilova, E. L. and Zakharov, K. and Koo, H-J and Pomjakushin, V. Yu and Susloparova, A. E. and et al.}, year={2020}, month={Sep} }
 @article{li_ni_li_koo_whangbo_feng_xiang_2020, title={Intralayer ferromagnetism between S=5/2 ions in MnBi2Te4: Role of empty Bi p states}, volume={101}, ISSN={["2469-9969"]}, DOI={10.1103/PhysRevB.101.201408}, abstractNote={The layered magnetic topological insulator MnBi$_2$Te$_4$ is a promising platform to realize the quantum anomalous Hall effect because its layers possess intrinsic ferromagnetism. However, it is not well understood why the high-spin $d^5$ magnetic ions Mn$^{2+}$ forming the Mn-Te-Mn spin exchange paths prefer ferromagnetic (FM) coupling, contrary to the prediction of the Goodenough-Kanamori rule that a TM-L-TM spin exchange, where TM and L are a transition-metal magnetic cation and a main group ligand, respectively, is antiferromagnetic (AFM) even when the bond angle of the exchange path is 90$^{\circ}$. Using density functional theory (DFT) calculations, we show that the presence of Bi$^{3+}$ ions is essential for the FM coupling in MnBi$_2$Te$_4$. Then, using a tight-binding model Hamiltonian, we find that high-spin $d^5$ ions (S = 5/2) in TM-L-TM spin exchange paths prefer FM coupling if the empty p-orbitals of a nonmagnetic cation M (e.g., Bi$^{3+}$ ion) hybridize strongly with those of the bridging ligand L, but AFM coupling otherwise.}, number={20}, journal={PHYSICAL REVIEW B}, author={Li, Jing and Ni, J. Y. and Li, X. Y. and Koo, H-J and Whangbo, M-H and Feng, J. S. and Xiang, H. J.}, year={2020}, month={May} }
 @article{cheng_li_wu_hong_whangbo_deng_2020, title={Key Factors Controlling the Large Second Harmonic Generation in Nonlinear Optical Materials}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.9b20023}, abstractNote={The second harmonic generation (SHG) responses of nonisostructural nonlinear optical (NLO) compounds, β-BaB2O4, LiB3O5, CsB3O5, CsLiB6O10, KBe2BO3F2, and LiCs2PO4, were examined by density functional theory (DFT) calculations, and the contributions of their individual cations and anions were determined by performing atomic response theory analyses. In all of these compounds, the contribution of all metal cations lies in the range of ∼9.3 to ∼29.7% of the total SHG responses, and that of all anions lies between ∼57.4 and ∼72.3%. However, in terms of individual atom contribution, a large metal cation can contribute more than does an anion to the total SHG response. Our work shows that the SHG contribution of an individual anion (e.g., O2–) is weakened when it forms covalent bonds with its surrounding cations (e.g., O–B). The contribution of an individual cation is further affected by the homogeneity of its surrounding anion distribution and also by how strongly the polarizabilities of its surrounding anions are weakened by covalent bonding with other cations. The SHG response increases with αsum/(NEg), an important parameter useful in searching for new NLO materials, where αsum is the sum of the polarizabilities of all of the ions in the primitive unit cell, N is the total number of atoms per primitive cell, and Eg is the band gap.}, number={8}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Cheng, Xiyue and Li, ZhenHua and Wu, Xin-Tao and Hong, Maochun and Whangbo, Myung-Hwan and Deng, Shuiquan}, year={2020}, month={Feb}, pages={9434–9439} }
 @article{yang_hu_wu_whangbo_radaelli_stroppa_2020, title={Magneto-Optical Kerr Switching Properties of (CrI3)(2) and (CrBr3/CrI3) Bilayers}, volume={2}, ISSN={["2637-6113"]}, DOI={10.1021/acsaelm.0c00154}, abstractNote={We explore the magneto-optical Kerr effect (MOKE) for different spin configurations of the (CrI3)2 bilayer and (CrBr3/CrI3) mixed bilayer using symmetry arguments and first-principles electronic structure calculations. Starting from CrX3 (X = I, Br) monolayers, we considered collinear ferromagnetic (FM) and layered antiferromagnetic (AFM) states for (CrI3)2 and (CrBr3/CrI3) bilayers. The AFM (CrI3)2 bilayer does not show MOKE, consistent with the presence of a symmetry operator combining inversion (I) and time reversal (T) symmetries. The FM state preserves I symmetry but breaks the T symmetry, thus allowing a nonzero Kerr angle, which is reversible by switching the FM spins. The (CrBr3/CrI3) bilayer breaks both the I and T symmetries and thus exhibits MOKE both in the FM state and, remarkably, in the AFM state. In both FM and AFM configurations, the Kerr angle switches by reversing the spins in both layers. Our study demonstrates that the MOKE spectra can help to characterize different magnetic configurations in these emerging two-dimensional (2D) magnetic materials due to a different stacking of the monolayers, even in the AFM case. Note that the present symmetry analyses and MOKE properties apply to more general 2D magnetic van der Waals heterostructures. Furthermore, we propose the (CrBr3/CrI3) bilayer as a promising candidate for AFM spintronics since the two time-reversed AFM states are associated with opposite Kerr rotation, i.e., they could be used as memory elements.}, number={5}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={Yang, Ke and Hu, Wentao and Wu, Hua and Whangbo, Myung-Hwan and Radaelli, Paolo Giuseppe and Stroppa, Alessandro}, year={2020}, month={May}, pages={1373–1380} }
 @article{wang_lv_zhou_liang_wang_liu_wang_zheng_dai_li_et al._2020, title={Molybdenum Nitride Electrocatalysts for Hydrogen Evolution More Efficient than Platinum/Carbon: Mo2N/CeO2@Nickel Foam}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c02851}, abstractNote={To produce hydrogen economically by electrolysis of water, one needs to develop a non-precious-metal catalyst that is as efficient as platinum metal. Here, we prepare such a catalyst by growing a layer of Mo2N over a layer of CeO2 deposited on nickel foam (NF) [hereafter, Mo2N /CeO2@NF] and show that the activity of this self-supported catalyst for hydrogen evolution in 1.0 M KOH is more efficient than that of the Pt/C electrode, achieving a current density of 10 mA/cm2 at a fairly low overpotential of 26 mV. Furthermore, after a long-time electrochemical stability test for 24 h at a fixed current density, the overpotential needed to attain a current density of 10 mA/cm2 is increased only by 6 mV, implying the huge potential of this method to prepare a super HER activity electrode for water splitting.}, number={26}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Wang, Cong and Lv, Xingshuai and Zhou, Peng and Liang, Xizhuang and Wang, Zeyan and Liu, Yuanyuan and Wang, Peng and Zheng, Zhaoke and Dai, Ying and Li, Yingjie and et al.}, year={2020}, month={Jul}, pages={29153–29161} }
 @article{koo_shankar_orlandi_sundaresan_whangbo_2020, title={On Ferro- and Antiferro-Spin-Density Waves Describing the Incommensurate Magnetic Structure of NaYNiWO6}, volume={59}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.0c02651}, abstractNote={The incommensurate magnetic structure (0.47, 0, 0.49) of NaYNiWO6 exhibits unconventional spin-density waves (SDWs) along the [100] direction, in which up and down spins alternate in each half-wave. This is in contrast to conventional SDWs, in which only one type of spin is present in each half-wave. We probed the formation of these unconventional SDWs by evaluating the spin exchanges of NaYNiWO6 based on density functional theory calculations and analyzing the nature of the spin frustration in NaYNiWO6 and by noting that a SDW is a superposition of two cycloids of opposite chirality. The unconventional SDWs along the [100] direction originate from the spin-frustrated antiferromagnetic chains of Ni2+ ions along that direction, leading to conventional SDWs along the [101] direction and unconventional SDWs along the [001] direction.}, number={24}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Shankar, Ravi P. N. and Orlandi, Fabio and Sundaresan, Athinarayanan and Whangbo, Myung-Hwan}, year={2020}, month={Dec}, pages={17856–17859} }
 @article{koo_kremer_whangbo_2020, title={Orbital Magnetic Moments of the High-Spin Co2+ Ions at Axially-Elongated Octahedral Sites: Unquenched as Reported from Experiment or Quenched as Predicted by Theory?}, volume={59}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.0c02929}, abstractNote={Neutron diffraction studies on magnetic solids composed of axially elongated CoO4X2 (X = Cl, Br, S, Se) octahedra show that the ordered magnetic moments of their high-spin Co2+ (d7, S = 3/2) ions are greater than 3 μB, i.e., the spin moment expected for S = 3/2 ions, and increase almost linearly from 3.22 to 4.45 μB as the bond-length ratio rCo-X/rCo-O increases from 1.347 to 1.659 where rCo-X and rCo-O are the Co-X and Co-O bond lengths, respectively. These observations imply that the orbital moments of the Co2+ ions increase linearly from 0.22 to 1.45 μB with increasing the rCo-X/rCo-O ratio from 1.347 to 1.659. We probed this implication by examining the condition for unquenched orbital moment and also by evaluating the magnetic moments of the Co2+ ions based on DFT+U+SOC calculations for those systems of the CoO4X2 octahedra. Our work shows that the orbital moments of the Co2+ ions are essentially quenched and, hence, that the observations of the neutron diffraction studies are not explained by the current theory of magnetic moments. This discrepancy between experiment and theory urges one to check the foundations of the current theory of magnetic moments as well as the current method of neutron diffraction refinements for ordered magnetic structures.}, number={24}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Kremer, Reinhard K. and Whangbo, Myung-Hwan}, year={2020}, month={Dec}, pages={18319–18324} }
 @article{vasilchikova_nalbandyan_shukaev_koo_whangbo_lozitskiy_bogaychuk_kuzmin_tagirov_vavilova_et al._2020, title={Peculiarities of magnetic ordering in the S=5/2 two-dimensional square-lattice antimonate NaMnSbO4}, volume={101}, ISSN={["2469-9969"]}, DOI={10.1103/PhysRevB.101.054435}, abstractNote={An orthorhombic compound, $\mathrm{NaMnSb}{\mathrm{O}}_{4}$, represents a square net of magnetic $\mathrm{M}{\mathrm{n}}^{2+}$ ions residing in vertex-shared oxygen octahedra. Its static and dynamic magnetic properties were studied using magnetic susceptibility, specific heat, magnetization, electron spin resonance (ESR), nuclear magnetic resonance (NMR), and density-functional calculations. Thermodynamic data indicate an establishment of the long-range magnetic order with ${T}_{\mathrm{N}}\ensuremath{\sim}44\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, which is preceded by a short-range one at about 55 K. In addition, a nontrivial wasp-waisted hysteresis loop of the magnetization was observed, indicating that the ground state is most probably canted antiferromagnetic. Temperature dependence of the magnetic susceptibility is described reasonably well in the framework of two-dimensional square-lattice model with the main exchange parameter $J=\ensuremath{-}5.3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, which is in good agreement with density-functional analysis, NMR, and ESR data.}, number={5}, journal={PHYSICAL REVIEW B}, author={Vasilchikova, Tatyana and Nalbandyan, Vladimir and Shukaev, Igor and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Lozitskiy, Andrey and Bogaychuk, Alexander and Kuzmin, Vyacheslav and Tagirov, Murat and Vavilova, Evgeniya and et al.}, year={2020}, month={Feb} }
 @article{maggard_chen_deng_whangbo_2020, title={Physical Properties of Molecules and Condensed Materials Governed by Onsite Repulsion, Spin-Orbit Coupling and Polarizability of their Constituent Atoms}, volume={25}, ISSN={["1420-3049"]}, url={https://www.mdpi.com/1420-3049/25/4/867}, DOI={10.3390/molecules25040867}, abstractNote={The onsite repulsion, spin–orbit coupling and polarizability of elements and their ions play important roles in controlling the physical properties of molecules and condensed materials. In celebration of the 150th birthday of the periodic table this year, we briefly review how these parameters affect the physical properties and are interrelated.}, number={4}, journal={Molecules}, author={Maggard, P.A. and Chen, X. and Deng, S. and Whangbo, M}, year={2020}, pages={867} }
 @article{jia_cheng_whangbo_hong_deng_2020, title={Second harmonic generation responses of KH2PO4: importance of K and breaking down of Kleinman symmetry}, volume={10}, ISSN={["2046-2069"]}, DOI={10.1039/d0ra03136d}, abstractNote={The second harmonic generation (SHG) responses of the paraelectric and ferroelectric phases of KH2PO4 (KDP) were calculated by first-principles density functional theory (DFT) calculations, and the individual atom contributions to the SHG responses were analyzed by the atom response theory (ART). We show that the occurrence of static polarization does not enhance the SHG responses of the ferroelectric KDP, and that the Kleinman symmetry is reasonably well obeyed for the paraelectric phase, but not for the ferroelectric phase despite that the latter has a larger bandgap. This is caused most likely by the fact that the ferroelectric phase has lower-symmetry local structures than does the paraelectric phase. The contribution to the SHG response of an individual K+ ion is comparable to that of an individual O2- ion. The contributions of the O2- and K+ ions arise overwhelmingly from the polarizable parts of the electronic structure, namely, from the valence bands of the O-2p nonbonding states and from the conduction bands of the K-3d states.}, number={44}, journal={RSC ADVANCES}, author={Jia, Minghao and Cheng, Xiyue and Whangbo, Myung-Hwan and Hong, Maochun and Deng, Shuiquan}, year={2020}, month={Jul}, pages={26479–26485} }
 @article{sorolla_wang_koo_whangbo_jacobson_2020, title={Synthesis of the Elusive S=1/2 Star Structure: A Possible Quantum Spin Liquid Candidate}, volume={142}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.0c00901}, abstractNote={Materials with two-dimensional, geometrically frustrated, spin-1/2 lattices provide a fertile playground for the study of intriguing magnetic phenomena such as quantum spin liquid (QSL) behavior, but their preparation has been a challenge. In particular, the long-sought, exotic spin-1/2 star structure has not been experimentally realized to date. Here we report the synthesis of [(CH3)2(NH2)]3[CuII3(μ3-OH)(μ3-SO4)(μ3-SO4)3]·0.24H2O with an S = 1/2 star lattice. On the basis of the magnetic susceptibility and heat capacity measurements, the layered Cu-based compound exhibits antiferromagnetic interactions but no magnetic ordering or spin freezing down to 2 K. The spin-frustrated material appears to be a promising QSL candidate.}, number={11}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Sorolla, Maurice, II and Wang, Xiqu and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Jacobson, Allan J.}, year={2020}, month={Mar}, pages={5013–5016} }
 @article{lee_kim_son_shim_whangbo_2020, title={Ternary selenides A(2)Sb(4)Se(8) (A = K, Rb and Cs) as an n-type thermoelectric material with high power factor and low lattice thermal conductivity: importance of the conformationally flexible Sb-Se-Se-Sb bridges}, volume={10}, ISSN={["2046-2069"]}, DOI={10.1039/d0ra01751e}, abstractNote={The ternary selenides A<sub>2</sub>Sb<sub>4</sub>Se<sub>8</sub> (A = K, Rb, Cs) are predicted to be a high-performance n-type thermoelectric material, and the conformationally-flexible Sb–Se(2)–Se(2)–Sb bridges are crucial in determining the thermoelectric properties of A<sub>2</sub>Sb<sub>4</sub>Se<sub>8</sub>.}, number={24}, journal={RSC ADVANCES}, author={Lee, Changhoon and Kim, Sujee and Son, Won-Joon and Shim, Ji-Hoon and Whangbo, Myung-Hwan}, year={2020}, month={Apr}, pages={14415–14421} }
 @article{cai_cheng_whangbo_hong_deng_2020, title={The partition principles for atomic-scale structures and their physical properties: application to the nonlinear optical crystal material KBe2BO3F2}, volume={22}, ISSN={["1463-9084"]}, DOI={10.1039/d0cp02755c}, abstractNote={In implementing the materials genome approach to search for new materials with interesting properties or functions, it is necessary to find the correct functional motif. To this end, it is common to partition an extended structure into various building units and then partition its properties to find the appropriate functional motif. We have developed the general principles for partitioning a structure and its properties in terms of a set of atoms and bonds by analyzing the differential cross-sections of neutron and X-ray scattering phenomena and proposed the procedures with which to partition an extended structure and its properties. We demonstrate how these procedures work by analyzing the nonlinear optical crystal KBe2BO3F2. Our partitioning analysis of KBe2BO3F2 leads to the conclusion that the second harmonic generation response of KBe2BO3F2 is dominated by the ionically bonded metal-centered groups.}, number={34}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Cai, Zewen and Cheng, Xiyue and Whangbo, Myung-Hwan and Hong, Maochun and Deng, Shuiquan}, year={2020}, month={Sep}, pages={19299–19306} }
 @article{golubev_nuss_kremer_gordon_whangbo_ritter_weber_wessel_2020, title={Two-dimensional magnetism in alpha-CuV2O6}, volume={102}, ISSN={["2469-9969"]}, DOI={10.1103/PhysRevB.102.014436}, abstractNote={Several previous studies reported that a one-dimensional Heisenberg chain model is inadequate in describing the magnetic properties of the low-dimensional quantum antiferromagnet $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$, but the origin for this observation has remained unclear. We have reinvestigated the magnetic properties of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ and found that our anisotropic magnetic susceptibility, neutron-powder diffraction, and electron paramagnetic spin-resonance measurements are in good agreement with extensive density-functional theory ($\mathrm{DFT}+U$) total energy calculations which indicate that the correct spin lattice model for $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ is rather a $S=1/2$ 2D-Heisenberg antiferromagnetic lattice. The magnetic susceptibility data are well described by a rectangular Heisenberg antiferromagnet with anisotropy ratio $\ensuremath{\alpha}\ensuremath{\sim}$ 0.7 consistent with the DFT results. Quantum Monte Carlo simulations of the magnetic susceptibilities for a rectangular lattice Heisenberg antiferromagnet were performed in the anisotropy range 0.5 $\ensuremath{\le}\ensuremath{\alpha}\ensuremath{\le}$ 1.0. The results of the Quantum Monte Carlo calculations were cast into a Pad\'e approximant which was used to fit the temperature-dependent magnetic susceptibility data. Neutron-powder-diffraction measurements were used to conclusively solve the collinear antiferromagnetic structure of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{CuV}}_{2}{\mathrm{O}}_{6}$ below the N\'eel temperature of $\ensuremath{\sim}22.4$ K.}, number={1}, journal={PHYSICAL REVIEW B}, author={Golubev, A. M. and Nuss, J. and Kremer, R. K. and Gordon, E. E. and Whangbo, M-H and Ritter, C. and Weber, L. and Wessel, S.}, year={2020}, month={Jul} }
 @article{cheng_whangbo_hong_deng_2019, title={Dependence of the Second-Harmonic Generation Response on the Cell Volume to Band-Gap Ratio}, volume={58}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.9b01368}, abstractNote={The second-harmonic generation (SHG) coefficients of 12 nonlinear optical chalcopyrites, ABC2 (A = Zn, Cd; B = Si, Ge, Sn; C = P, As) were calculated by first-principles methods to find that given the primitive cell volume V and the band gap Eg of ABC2, the SHG coefficients dav of ABC2 increase almost linearly with increasing value of V/Eg. This suggests that a noncentrosymmetric crystal has a large SHG response when it consists of large atoms, leading to a small band gap.}, number={15}, journal={INORGANIC CHEMISTRY}, author={Cheng, Xiyue and Whangbo, Myung-Hwan and Hong, Maochun and Deng, Shuiquan}, year={2019}, month={Aug}, pages={9572–9575} }
 @article{koo_whangbo_2019, title={Effect of Nonmagnetic Ion Deficiency on Magnetic Structure: Density Functional Study of Sr2MnO2Cu2-xTe2, Sr2MO2Cu2Te2 (M = Co, Mn), and the Oxide-Hydrides Sr2VO3H, Sr3V2O5H2, and SrVO2H}, volume={58}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.9b02456}, abstractNote={Two seemingly puzzling observations on two magnetic systems were analyzed. For the oxide-hydrides Sr2VO3H, Sr3V2O5H2, and SrVO2H, made up of VO4H2 octahedra, the spin orientations of the V3+ (d2, S = 1) ions were reported to be different, namely, perpendicular to the H-V-H bond in Sr2VO3H but parallel to the H-V-H bond in Sr3V2O5H2 and SrVO2H, despite that the d-state split patterns of the VO4H2 octahedra are similar in the three oxide-hydrides. Another puzzling observation is the contrasting magnetic structures of Sr2CoO2Cu2Te2 and Sr2MnO2Cu1.58Te2, consisting of the layers made up of corner-sharing MO4Te2 (M = Co, Mn) octahedra. The Co2+ spins in each CoO2Te2 layer are antiferromagnetically coupled with spins perpendicular to the Te-Co-Te bond, whereas the Mn3+/Mn2+ ions of each MnO2Te2 layer are ferromagnetically coupled with spins parallel to the Te-Mn-Te bonds. We investigated the cause for these observations by performing first-principles density functional theory (DFT) calculations for stoichiometric phases Sr2VO3H, Sr3V2O5H2, SrVO2H, Sr2CoO2Cu2Te2, and Sr2MnO2Cu2Te2, as well as nonstoichiometric phase Sr2MnO2Cu1.5Te2. Our study reveals that the V3+ ions in all three oxide-hydrides should have the spin orientation parallel to the H-V-H bond. The unusual magnetic structure of the MnO2Te2 layers of Sr2MnO2Cu1.52Te2 arises from the preference of a Mn3+ spin to be parallel to the Te-Mn-Te bond, the ferromagnetic spin exchange between adjacent Mn3+ and Mn2+ ions, and the nearly equal numbers of Mn3+ and Mn2+ ions in each MnO2Te2 layer. We show that the spin orientation of the magnetic ions in an antiferromagnetically coupled perovskite layer, expected in the absence of nonmagnetic ion vacancies, cannot be altered by the magnetic ions of higher oxidation that result from trace vacancies at the nonmagnetic ion sites.}, number={21}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2019}, month={Nov}, pages={14769–14776} }
 @article{li_jin_wang_liu_wang_zheng_whangbo_kou_li_dai_et al._2019, title={Effect of the intra- and inter-triazine N-vacancies on the photocatalytic hydrogen evolution of graphitic carbon nitride}, volume={369}, ISBN={1873-3212}, DOI={10.1016/j.cej.2019.03.095}, abstractNote={Abstract We developed a new method to introduce N-vacancies of graphitic carbon nitride (GCN, typically in the Melon structure) at the inter-triazine sites and investigated how the visible-light photocatalytic H2 evolution of GCN is affected by the N-vacancies at the intra- and inter-triazine sites of GCN. Theoretical and experimental results show that these N-vacancies of GCN create singly-occupied defect states within the band gap acting as a trap for photogenerated electrons and act as the reaction sites for H+ reduction. Compared with the intra-triazine N-vacancy, the inter-triazine N-vacancy exhibits stronger electron localization leading to a more efficient H2 evolution. The photocatalytic reaction rate of GCN with inter-triazine N-vacancies is 9 times higher than that of “defect free” GCN, and 2.2 times higher normalized reaction rates than GCN with intra-triazine N-vacancies. The catalysis mechanism and the method to prepare melon with inter-triazine N-vacancies can be extended to explore new photocatalysts with high activities.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Li, Huiliang and Jin, Cui and Wang, Zeyan and Liu, Yuanyuan and Wang, Peng and Zheng, Zhaoke and Whangbo, Myung-Hwan and Kou, Liangzhi and Li, Yingjie and Dai, Ying and et al.}, year={2019}, pages={263–271} }
 @article{whangbo_xiang_koo_gordon_whitten_2019, title={Electronic and Structural Factors Controlling the Spin Orientations of Magnetic Ions}, volume={58}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/acs.inorgchem.9b00687}, DOI={10.1021/acs.inorgchem.9b00687}, abstractNote={Magnetic ions M in discrete molecules and extended solids form MLn complexes with their first-coordinate ligand atoms L. The spin moment of M in a complex MLn prefers a certain direction in coordinate space because of spin–orbit coupling (SOC). In this minireview, we examine the structural and electronic factors governing the preferred spin orientations. Elaborate experimental measurements and/or sophisticated computational efforts are required to find the preferred spin orientations of magnetic ions, largely because the energy scale of SOC is very small. The latter is also the very reason why one can readily predict the preferred spin orientation of M by analyzing the SOC-induced highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) interactions of the MLn complexes in terms of qualitative perturbation theory. The strength of this HOMO–LUMO interaction depends on the spin orientation, which is governed by the selection rules based on the minimum |ΔLz| value (i.e., the minimum difference in the magnetic quantum numbers) between the HOMO and LUMO. With the local z axis of MLn chosen as its n-fold rotational axis, the preferred spin orientation is parallel to the z axis (∥z) when |ΔLz| = 0 but perpendicular to the z axis (⊥z) when |ΔLz| = 1.}, number={18}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Whangbo, Myung-Hwan and Xiang, Hongjun and Koo, Hyun-Joo and Gordon, Elijah E. and Whitten, Jerry L.}, year={2019}, month={Jun}, pages={11854–11874} }
 @article{gao_li_zhou_wang_zheng_wang_liu_dai_whangbo_huang_2019, title={Enhanced selectivity and activity for electrocatalytic reduction of CO2 to CO on an anodized Zn/carbon/Ag electrode}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c9ta04529e}, abstractNote={The selectivity and activity of the anodized Zn/C/Ag composite electrode containing a tiny amount of Ag (∼0.5 wt%) are enhanced by the synergistic effect of Zn, C and Ag.}, number={28}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Gao, Yugang and Li, Fengping and Zhou, Peng and Wang, Zeyan and Zheng, Zhaoke and Wang, Peng and Liu, Yuanyuan and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2019}, month={Jul}, pages={16685–16689} }
 @article{an_liu_bian_wang_wang_zheng_dai_whangbo_huang_2019, title={Improving the photocatalytic hydrogen evolution of UiO-67 by incorporating Ce4+-coordinated bipyridinedicarboxylate ligands}, volume={64}, ISSN={["2095-9281"]}, DOI={10.1016/j.scib.2019.07.030}, abstractNote={UiO-67 is a Zr-based metal–organic framework (MOF) containing an organic linker namely, the dianion of biphenyl-4,4′-dicarboxylic acid (bpdc). Ce4+ metal ions (0.02 Ce to Zr atom ratio) were incorporated into UiO-67 via partially replacing bpdc with the dianion of 2,2′-bipyridine-5,5′-dicarboxylic acid (bpydc); thus, the latter forms a bpydc-Ce complex. The resulting product (i.e., UiO-67-Ce) demonstrated a photocatalytic hydrogen evolution rate that was over 10 times higher than that of UiO-67. Through this modification, a new energy transfer channel is opened up. The energy transfer between the bpdc and bpydc-Ce ligands (i.e., from excited bpdc to bpydc-Ce) weakened the recombination of the charge carriers, which was confirmed by photoluminescence, emission lifetime, and transient absorption measurements. This study presents a new way to construct highly efficient MOF photocatalysts.}, number={20}, journal={SCIENCE BULLETIN}, author={An, Yang and Liu, Yuanyuan and Bian, Hongtao and Wang, Zeyan and Wang, Peng and Zheng, Zhaoke and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2019}, month={Oct}, pages={1502–1509} }
 @article{guan_wu_wang_zhang_wang_zheng_liu_dai_whangbo_huang_2019, title={Perovskite photocatalyst CsPbBr3-xIx with a bandgap funnel structure for H-2 evolution under visible light}, volume={245}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2019.01.019}, abstractNote={A simple and efficient light-assisted method is employed to prepare powder samples of all-inorganic mixed-perovskite CsPbBr3-xIx from CsPbBr3 by ion exchange in aqueous HBr/KI solution such that the concentration of I in a sample particle decreases on going from the surface to the interior. CsPbBr3-xIx/Pt, namely, CsPbBr3-xIx samples loaded with Pt nanoparticles, shows a high performance for the hydrogen evolution under visible-light irradiation in aqueous HBr solution saturated with CsPbBr3. The H2 evolution rate of the CsPbBr3-xIx/Pt powders (200 mg) is determined to be 224 μmol h−1, under 120 mW cm-2 visible-light (λ ≥ 420 nm) illumination. The CsPbBr3-xIx samples have a high stability, with no apparent decrease in the catalytic activity after 50 h of repeated H2 evolution experiments. The apparent quantum efficiency of CsPbBr3-xIx/Pt is determined to be 2.15% under the irradiation of 450 nm light.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Guan, Zihan and Wu, Yaqiang and Wang, Peng and Zhang, Qianqian and Wang, Zeyan and Zheng, Zhaoke and Liu, Yuanyuan and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2019}, month={May}, pages={522–527} }
 @article{zhang_liu_wang_wang_zheng_qin_zhang_dai_whangbo_huang_2019, title={Selective photocatalytic conversion of alcohol to aldehydes by singlet oxygen over Bi-based metal-organic frameworks under UV-vis light irradiation}, volume={254}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2019.05.024}, abstractNote={So far, most efforts in photocatalysis have been devoted to the separation of photogenerated electron-hole pairs, and possible use of excitons (i.e., electron-hole pairs) for photocatalytic processes has not received much attention. In this work, we studied the effect of metal dots on the excitonic behaviors of two bismuth-based MOFs, Bi-TATB and Bi-BTC (here the tridentate ligands TATB3− and BTC3− represent the carboxylates of 4,4′,4′'-s-triazine-2,4,6-triyl-tribenzoic and 1,3,5-benzenetricarboxylic acids, respectively). The organic ligands (TATB and BTC) display different emission properties from the corresponding Bi based MOFs. Specifically, TATB and BTC display strong fluorescence emission while Bi-TATB and Bi-BTC display strong phosphorescence emission, suggesting the higher efficiency of intersystem crossing for Bi-TATB and Bi-BTC. The reason is attributed to the coordination with Bi, which promotes the singlet→ triplet intersystem crossing of the organic ligand due to the heavy metal effect. The enhanced triplet excited emission of Bi-TATB and Bi-BTC was further confirmed by the detection of 1O2, as 1O2 is well known to be formed due to energy transfer from the triplet state of photosensitizers to the ground-state oxygen (3O2). With above understanding, Bi-TATB and Bi-BTC were finally used to high selective photooxidation of benzyl alcohol to benzaldehyde. This work presents new understanding of the photophysical properties of Bi based MOFs, which provides alternative ideas on designing materials for selective photo-oxidation.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Zhang, Ruoqian and Liu, Yuanyuan and Wang, Zeyan and Wang, Peng and Zheng, Zhaoke and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2019}, month={Oct}, pages={463–470} }
 @article{an_liu_wang_wang_zheng_dai_qin_zhang_whangbo_huang_2019, title={Stabilizing the titanium-based metal organic frameworks in water by metal cations with empty or partially-filled d orbitals}, volume={533}, ISSN={["1095-7103"]}, DOI={10.1016/j.jcis.2018.08.049}, abstractNote={Though titanium-based metal-organic frameworks (MOFs) are declared to be relatively water stable, their framework gradually collapses in water within days due to the attack of OH− to OTiO bond. For practical applications of titanium-based MOFs, it is crucial to solve their instability problem in water. We searched for a simple and efficient method to enhance the stability of titanium-based MOFs in water by using Ti-ATA (ATA = 2-aminoterephthallate ion) as a representative titanium-based MOF. Here, we show that the stability of Ti-ATA in water is greatly improved nearly without affecting its porosity and photocatalytic activity by treating it with aqueous solutions containing metal ions of empty d orbitals (Y3+, La3+, Ce3+, Nd3+ and Tm3+) or partially-filled d orbitals (Cr3+).}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={An, Yang and Liu, Yuanyuan and Wang, Zeyan and Wang, Peng and Zheng, Zhaoke and Dai, Ying and Qin, Xiaoyan and Zhang, Xiaoyang and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2019}, month={Jan}, pages={9–12} }
 @article{uma_vasilchikova_sobolev_raganyan_sethi_koo_whangbo_presniakov_glazkova_vasiliev_et al._2019, title={Synthesis and Characterization of Sodium-Iron Antimonate Na2FeSbO5: One-Dimensional Antiferromagnetic Chain Compound with a Spin-Glass Ground State}, volume={58}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.9b00212}, abstractNote={A new oxide, sodium iron antimonate, Na2FeSbO5, was synthesized and structurally characterized, and its static and dynamic magnetic properties were comprehensively studied both experimentally by dc and ac magnetic susceptibility, magnetization, specific heat, electron spin resonance (ESR) and Moessbauer measurements, and theoretically by density functional calculations. The resulting single-crystal structure (a = 15.6991(9) A; b = 5.3323 (4) A; c = 10.8875(6) A; S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The 57Fe Moessbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in a distorted tetrahedral oxygen coordination. The magnetic susceptibility and specific heat data show the absence of a long-range magnetic ordering in Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates spin-glass-type behavior with a unique two-step freezing at Tf1 about 80 K and Tf2 about 35 K. Magnetic hyperfine splitting of 57Fe Moessbauer spectra was observed below T* about 104 K (Tf1 < T*). The spectra just below T* (Tf1 < T < T*) exhibit a relaxation behavior caused by critical spin fluctuations, indicating the existence of short-range correlations. The stochastic model of ionic spin relaxation was used to account for the shape of the Moessbauer spectra below the freezing temperature. A complex slow dynamics is further supported by ESR data revealing two different absorption modes presumably related to ordered and disordered segments of spin chains. The data imply a spin-cluster ground state for Na2FeSbO5.}, number={17}, journal={INORGANIC CHEMISTRY}, author={Uma, Sitharaman and Vasilchikova, Tatyana and Sobolev, Alexey and Raganyan, Grigory and Sethi, Aanchal and Koo, Hyun-Joo and Whangbo, Myun-Hwan and Presniakov, Igor and Glazkova, Iana and Vasiliev, Alexander and et al.}, year={2019}, month={Sep}, pages={11333–11350} }
 @article{koo_kasapbasi_whitten_whangbo_2019, title={The Conceptual Dilemma of the One-Electron Picture in Describing the Uniaxial Magnetism at Linear Coordination Sites}, volume={2019}, ISSN={1434-1948}, url={http://dx.doi.org/10.1002/ejic.201900370}, DOI={10.1002/ejic.201900370}, abstractNote={High‐spin Fe 2+ , Fe + and Co 2+ ions at linear two‐coordination sites exhibit uniaxial magnetism. In the one‐electron picture, the uniaxial magnetism of the Fe 2+ ion is explained, while those of the Fe + and Co 2+ ions are not, if the d‐state split pattern is 1e < 2e < 1a. The opposite is true if the d‐state split pattern is 1a < 1e < 2e. We resolved this conceptual dilemma by evaluating the relative stabilities for the various L states of linear molecules (Fe L 2 ) 0 , (Fe L 2 ) – , and (Co L 2 ) 0 with L = C(SiH 3 ) 3 on the basis of first‐principles broken‐symmetry and configuration interaction calculations. In the first‐principles picture, the total energy of an electron configuration depends not only on the energy sequence of the occupied d‐states, as do the one‐electron picture, but also on the electron repulsion between occupied d‐states, which is neglected by the one‐electron picture.}, number={21}, journal={European Journal of Inorganic Chemistry}, publisher={Wiley}, author={Koo, Hyun-Joo and Kasapbasi, Esra E. and Whitten, Jerry L. and Whangbo, Myung-Hwan}, year={2019}, month={May}, pages={2630–2634} }
 @article{chi_xu_xue_zhang_chen_whangbo_guo_deng_2019, title={Triple-Kagome-Layer Slabs of Mixed-Valence Rare-Earth Ions Exhibiting Quantum Spin Liquid Behaviors: Synthesis and Characterization of Eu9MgS2B20O41}, volume={141}, ISSN={["0002-7863"]}, DOI={10.1021/jacs.9b04627}, abstractNote={We prepared a new rare-earth compound, Eu9MgS2B20O41 (EMSBO), and characterized its structural and physical properties. EMSBO consists of triple-Kagomé-layer slabs separated by nonmagnetic ions and groups. Within each slab, intervalence charge transfer has been found to occur between the Eu2+ and Eu3+ Kagomé layers, a new channel for quantum fluctuation of magnetic moments. The measured magnetic susceptibilities and the specific heat capacity exhibit very similar features characteristic of quantum spin liquid behaviors observed in other materials.}, number={24}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Chi, Yang and Xu, Jing and Xue, Huai-Guo and Zhang, Yueping and Chen, Xiaolong and Whangbo, Myung-Hwan and Guo, Sheng-Ping and Deng, Shuiquan}, year={2019}, month={Jun}, pages={9533–9536} }
 @article{liang_wang_li_zhang_wang_dai_zhang_liu_whangbo_huang_2018, title={Adsorption of gaseous ethylene via induced polarization on plasmonic photocatalyst Ag/AgCl/TiO2 and subsequent photodegradation}, volume={220}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2017.07.075}, abstractNote={Abstract The removal of nonpolar gaseous ethylene molecules on the plasmonic photocatalyst Ag/AgCl/TiO2 was examined under simulated sunlight irradiation, to find that it has a markedly high activity for the oxidation of ethylene molecules. Systematic experiments, carried out to probe the cause for this observation, indicate that the strong electric field mainly on the Ag nanoparticles (NPs) generated by their surface plasmon resonance (SPR) induces polarization in gaseous ethylene molecules hence enhancing their adsorption on the catalysts and their subsequent photodegradation, and that TiO2 acts as a substrate for dispersing Ag/AgCl nanoparticles to have a larger active surface area. This study provides new ideas towards designing advanced photocatalysts for the degradation of nonpolar gaseous molecules.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Liang, Xizhuang and Wang, Peng and Li, Mengmeng and Zhang, Qianqian and Wang, Zeyan and Dai, Ying and Zhang, Xiaoyang and Liu, Yuanyuan and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2018}, month={Jan}, pages={356–361} }
 @article{zhu_wang_wang_liu_zheng_zhang_zhang_dai_whangbo_huang_2018, title={Co3O4 nanobelt arrays assembled with ultrathin nanosheets as highly efficient and stable electrocatalysts for the chlorine evolution reaction}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta03689f}, abstractNote={We report Co<sub>3</sub>O<sub>4</sub> nanobelt arrays (NBAs) assembled with ultrathin nanosheets prepared on fluorine doped tin oxide (FTO) substrates as electrocatalysts for the CER.}, number={26}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Zhu, Xianglin and Wang, Peng and Wang, Zeyan and Liu, Yuanyuan and Zheng, Zhaoke and Zhang, Qianqian and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2018}, month={Jul}, pages={12718–12723} }
 @article{lee_kim_tak_cho_shim_lim_whangbo_2018, title={Comparison of the electronic and thermoelectric properties of three layered phases Bi2Te3, PbBi2Te4 and PbBi4Te7: LEGO thermoelectrics}, volume={8}, ISSN={["2158-3226"]}, DOI={10.1063/1.5047823}, abstractNote={The electronic and thermoelectric properties of Bi2Te3, PbBi2Te4 and PbBi4Te7 were examined on the basis of density functional theory (DFT) calculations and thermoelectric transport property measurements. The layered phase PbBi4Te7 is composed of the slabs forming the layered phases Bi2Te3 and PbBi2Te4. The electronic structure of PbBi4Te7 around the valence band maximum and conduction band minimum exhibits those of Bi2Te3 and PbBi2Te4. The band gap of PbBi4Te7 lies in between those of Bi2Te3 and PbBi2Te4, and the density of states of PbBi4Te7 is well approximated by the sum of those of Bi2Te3 and PbBi2Te4. In terms of the carrier concentration, the carrier mobility, the carrier lifetime, the electrical conductivity normalized to the carrier lifetime, and the effective mass, the layered phases Bi2Te3, PbBi4Te7 and PbBi2Te4 form a group of thermoelectrics, which have the structures composed of several different slabs and whose thermoelectric properties are approximated by the average of those of the constituent slabs. We propose to use the term “LEGO thermoelectrics” to describe such a family of thermoelectric materials that operate in a desired temperature range and possess predictable thermoelectric properties.}, number={11}, journal={AIP ADVANCES}, author={Lee, Changhoon and Kim, Jae Nyeong and Tak, Jang-Yeul and Cho, Hyung Koun and Shim, Ji Hoon and Lim, Young Soo and Whangbo, Myung-Hwan}, year={2018}, month={Nov} }
 @article{wu_wang_zhu_zhang_wang_liu_zou_dai_whangbo_huang_2018, title={Composite of CH3NH3PbI3 with reduced graphene oxide as a highly efficient and stable visible-light photocatalyst for hydrogen evolution in aqueous HI solution}, volume={30}, number={7}, journal={Advanced Materials}, author={Wu, Y. Q. and Wang, P. and Zhu, X. L. and Zhang, Q. Q. and Wang, Z. Y. and Liu, Y. Y. and Zou, G. Z. and Dai, Y. and Whangbo, M. H. and Huang, B. B.}, year={2018} }
 @article{lou_zhu_yang_zhang_whangbo_li_huang_2018, title={Continual injection of photoinduced electrons stabilizing surface plasmon resonance of non-elemental-metal plasmonic photocatalyst CdS/WO3-x for efficient hydrogen generation}, volume={226}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2017.12.023}, abstractNote={To remedy the instability problem of the non-elemental-metal (NEM) plasmonic photocatalyst WO3−x in aqueous solution, a novel strategy of photoinduced electron injection was applied to construct CdS/WO3−x hetereostructures by growing WO3−x on semiconductor CdS nanowires. Under visible/near-infrared light irradiation, the NEM plasmonic CdS/WO3−x nanowires are highly stable and exhibit a much higher activity (1.60 mmol g−1 h−1) than do plasmonic WO3−x (negligible amount) and semiconductor CdS (0.53 mmol g−1 h−1) in hydrogen generation. Wavelength dependent photocatalytic performance and Single-particle PL study demonstrate that photo-excited electrons on CdS continually inject into conduction band of WO3−x, so that the surface plasmon resonance (SPR) of the NEM plasmonic photocatalyst WO3−x is sustained while hot electrons generated by the SPR excitation are consumed for hydrogen generation.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Lou, Zaizhu and Zhu, Mingshan and Yang, Xianguang and Zhang, Yao and Whangbo, Myung-Hwan and Li, Baojun and Huang, Baibiao}, year={2018}, month={Jun}, pages={10–15} }
 @article{li_zhang_wang_wang_liu_zhang_qin_dai_whangbo_huang_2018, title={Endotaxial growth of [100]-oriented TaON films on LiTaO3 single crystals for enhanced photoelectrochemical water splitting}, volume={2}, number={6}, journal={Solar RRL}, author={Li, H. L. and Zhang, B. and Wang, Z. Y. and Wang, P. and Liu, Y. Y. and Zhang, X. Y. and Qin, X. Y. and Dai, Y. and Whangbo, M. H. and Huang, B. B.}, year={2018} }
 @article{wu_wang_guan_liu_wang_zheng_jin_dai_whangbo_huang_2018, title={Enhancing the Photocatalytic Hydrogen Evolution Activity of Mixed-Halide Perovskite CH3NH3PbBr3-xIx Achieved by Bandgap Funneling of Charge Carriers}, volume={8}, ISSN={["2155-5435"]}, DOI={10.1021/acscatal.8b02374}, abstractNote={Powder samples of mixed halide perovskite MAPbBr3–xIx (MA = methylammonium ion, CH3NH3+) were prepared by employing a facile light-assisted halide-exchange method in aqueous halide solution at room temperature. It is found that the distribution of iodide ions in the MAPbBr3–xIx particles tends to be largest on the surface and becomes lower on going into the interior so that they have a correct bandgap funnel structure that is needed for transferring photogenerated charge carriers from the interior to the surface. Consequently, the MAPbBr3–xIx/Pt powder sample (250 mg) exhibits an enhanced photocatalytic activity for a H2 evolution under visible light (100 mW cm–2, λ ≥ 420 nm) with the rate of 651.2 μmol h–1 and a solar-to-chemical conversion efficiency of 1.05%.}, number={11}, journal={ACS CATALYSIS}, author={Wu, Yaqiang and Wang, Peng and Guan, Zihan and Liu, Junxue and Wang, Zeyan and Zheng, Zhaoke and Jin, Shengye and Dai, Ying and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2018}, month={Nov}, pages={10349–10357} }
 @article{lomnytska_dzevenko_babizhetskyy_toma_smolyak_gordon_whangbo_koehler_2018, title={Interaction of tantalum, titanium and phosphorus at 1070 K: Phase diagram and structural chemistry}, volume={732}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2017.10.247}, abstractNote={Abstract The solid state phase diagram for the equilibria of the ternary Ta-Ti-P system was established by X-ray powder diffraction at T = 1070 K in the region up to 67 at.% P. Isostructural compounds Ta3P and Ti3P (both Ti3P-type) form a continuous series of substitution-type solid solutions. The majority of binary compounds form substitution-type solid solutions, in which the substitution of Ti for Ta, or Ta for Ti, takes place. The crystal structure investigation of the new ternary phosphide demonstrates that this phase is isotypical to the OsGe2 structure type and has a small homogeneity range, which can be described by the formula Та1-xТіxР2 (x = 0.07(3)−0.145(7), space group C2/m, a = 8.8556(9)−8.8446(2), b = 3.2654(4)−3.2605(1), c = 7.4846(8)−7.4741(1) A, β = 119.307(2)−119.308(1)°). Our density functional theory (DFT) electronic structure calculations show that the stoichiometric composition TaP2 has no electronic instability, although it does not exist under the thermal conditions used in present study. The addition of a small amount of Ti leads to a ternary phase Та1-xТіxР2 (x = 0.07(3)−0.145(7)) with a higher thermal stability compared to TaP2.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Lomnytska, Ya. and Dzevenko, M. and Babizhetskyy, V. and Toma, O. and Smolyak, O. and Gordon, E. E. and Whangbo, M. -H. and Koehler, J.}, year={2018}, month={Jan}, pages={777–783} }
 @article{whangbo_deng_koehler_simon_2018, title={Interband Electron Pairing for Superconductivity from the Breakdown of the Born-Oppenheimer Approximation}, volume={19}, ISSN={["1439-7641"]}, DOI={10.1002/cphc.201800738}, abstractNote={The origin of interband electron pairing responsible for enhancing superconductivity and the factors controlling its strength were examined. We show that the interband electron pairing is a natural consequence of breaking down the Born-Oppenheimer approximation during the electron-phonon interactions. Its strength is determined by the pair-state excitations around the Fermi surfaces that take place to form a superconducting state. Fermi surfaces favorable for the pairing were found and its implications were discussed.}, number={23}, journal={CHEMPHYSCHEM}, author={Whangbo, Myung-Hwan and Deng, Shuiquan and Koehler, Juergen and Simon, Arndt}, year={2018}, month={Dec}, pages={3191–3195} }
 @article{golubev_bruecher_schulz_kremer_schmidt_gordon_whangbo_2018, title={Low-Dimensional Magnetic Properties of Natural and Synthetic Mixite (Bi,Ca)Cu-6(OH)(6)(AsO4)(3)center dot nH(2)O (n approximate to 3) and Goudeyite YCu6(OH)(6)(AsO4)(3)center dot nH(2)O (n approximate to 3)}, volume={644}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.201800344}, abstractNote={The structural, vibrational, and especially the magnetic properties of natural and synthetic polycrystalline samples of the minerals mixite with composition (Bi,Ca)Cu 6 (OH) 6 (AsO 4 ) 3 · n H 2 O ( n ≈ 3) and goudeyite with composition YCu 6 (OH) 6 (AsO 4 ) 3 · n H 2 O ( n ≈ 3) were investigated. The magnetic susceptibilities are characterized by low‐dimensional antiferromagnetic short range ordering and can be well fitted by the theoretical susceptibilities of a spin S = 1/2 alternating Heisenberg chain with nearest‐neighbor spin exchange ranging between 200 K and 130 K for natural mixite and synthetic goudeyite, respectively. The alternation parameters, i.e. the ratios of nearest and next‐nearest neighbor spin exchange range between 0.52 for natural mixite and 0.75 for synthetic mixite and goudeyite, respectively. The experimentally observed spin exchange parameters are consistent with DFT calculations of the spin exchange parameters.}, number={24}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Golubev, Aleksandr and Bruecher, Eva and Schulz, Armin and Kremer, Reinhard K. and Schmidt, Franz X. and Gordon, Elija E. and Whangbo, Myung-Hwan}, year={2018}, month={Dec}, pages={1782–1790} }
 @article{leiner_oh_kolesnikov_stone_le_kenny_powell_mourigal_gordon_whangbo_et al._2018, title={Magnetic excitations of the Cu2+ quantum spin chain in Sr3CuPtO6}, volume={97}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.97.104426}, abstractNote={We report the magnetic excitation spectrum as measured by inelastic neutron scattering for a polycrystalline sample of ${\mathrm{Sr}}_{3}{\mathrm{CuPtO}}_{6}$. Modeling the data by the 2+4 spinon contributions to the dynamical susceptibility within the chains, and with interchain coupling treated in the random phase approximation, accounts for the major features of the powder-averaged structure factor. The magnetic excitations broaden considerably as temperature is raised, persisting up to above 100 K and displaying a broad transition as previously seen in the susceptibility data. No spin gap is observed in the dispersive spin excitations at low momentum transfer, which is consistent with the gapless spinon continuum expected from the coordinate Bethe ansatz. However, the temperature dependence of the excitation spectrum gives evidence of some very weak interchain coupling.}, number={10}, journal={PHYSICAL REVIEW B}, author={Leiner, J. C. and Oh, Joosung and Kolesnikov, A. I. and Stone, M. B. and Le, Manh Duc and Kenny, E. P. and Powell, B. J. and Mourigal, M. and Gordon, E. E. and Whangbo, M. -H. and et al.}, year={2018}, month={Mar} }
 @article{gordon_cheng_kim_cheong_deng_whangbo_2018, title={Nonequivalent Spin Exchanges of the Hexagonal Spin Lattice Affecting the Low-Temperature Magnetic Properties of RInO3 (R = Gd, Tb, Dy): Importance of Spin-Orbit Coupling for Spin Exchanges between Rare-Earth Cations with Nonzero Orbital Moments}, volume={57}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.8b01274}, abstractNote={Rare-earth indium oxides RInO3 (R = Gd, Tb, Dy) consist of spin-frustrated hexagonal spin lattices made up of rare-earth ions R3+, where R3+ = Gd3+ (f7, L = 0), Tb3+ (f8, L = 3), and Dy3+ (f9, L = 5). We carried out DFT calculations for RInO3, including on-site repulsion U with/without spin–orbit coupling (SOC), to explore if their low-temperature magnetic properties are related to the two nonequivalent nearest-neighbor (NN) spin exchanges of their hexagonal spin lattices. Our DFT + U + SOC calculations predict that the orbital moments of the Tb3+ and Dy3+ ions are smaller than their free-ion values by ∼2μB while the Tb3+ spins have an in-plane magnetic anisotropy, in agreement with the experiments. This suggests that the f orbitals of each R3+ (R = Tb, Dy) ion are engaged, though weakly, in bonding with the surrounding ligand atoms. The magnetic properties of GdInO3 with the zero orbital moment are adequately described by the spin exchanges extracted by DFT + U calculations. In describing the magnetic properties of TbInO3 and DyInO3 with nonzero orbital moments, however, the spin exchanges extracted by DFT + U + SOC calculations are necessary. The spin exchanges of RInO3 (R = Gd, Tb, Dy) are dominated by the two NN spin exchanges J1 and J2 of their hexagonal spin lattice, in which the honeycomb lattice of J2 forms spin-frustrated (J1, J1, J2) triangles. The J2/J1 ratios are calculated to be ∼3, ∼1.7, and ∼1 for GdInO3, TbInO3, and DyInO3, respectively. This suggests that the antiferromagnetic (AFM) ordering of GdInO3 below 1.8 K is most likely an AFM ordering of its honeycomb spin lattice and that TbInO3 would exhibit low-temperature magnetic properties similar to those of GdInO3 while DyInO3 would not.}, number={15}, journal={INORGANIC CHEMISTRY}, author={Gordon, Elijah E. and Cheng, Xiyue and Kim, Jaewook and Cheong, Sang-Wook and Deng, Shuiquan and Whangbo, Myung-Hwan}, year={2018}, month={Aug}, pages={9260–9265} }
 @article{gordon_derakhshan_thompson_whangho_2018, title={Spin-Density Wave as a Superposition of Two Magnetic States of Opposite Chirality and Its Implications}, volume={57}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.8b01494}, abstractNote={A magnetic solid with weak spin frustration tends to adopt a noncollinear magnetic structure such as a cycloidal structure below a certain temperature and a spin-density wave (SDW) slightly above this temperature. The causes for these observations were explored by studying the magnetic structure of BaYFeO4, which undergoes a SDW and a cycloidal phase transition below 48 and 36 K, respectively, in terms of the density functional theory calculations. We show that a SDW structure arises from a superposition of two magnetic states of opposite chirality, an SDW state precedes a chiral magnetic state because of the lattice relaxation, and whether a SDW is transversal or longitudinal is governed by the magnetic anisotropy of magnetic ions.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Gordon, Elijah E. and Derakhshan, Shahab and Thompson, Corey M. and Whangho, Myung-Hwan}, year={2018}, month={Aug}, pages={9782–9785} }
 @article{cheng_whangbo_guo_hong_deng_2018, title={The Large Second-Harmonic Generation of LiCs2PO4 is caused by the Metal-Cation-Centered Groups}, volume={57}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201711465}, abstractNote={Abstract We evaluated the individual atom contributions to the second harmonic generation (SHG) coefficients of LiCs 2 PO 4 (LCPO) by introducing the partial response functionals on the basis of first principles calculations. The SHG response of LCPO is dominated by the metal‐cation‐centered groups CsO 6 and LiO 4 , not by the nonmetal‐cation‐centered groups PO 4 expected from the existing models and theories. The SHG coefficients of LCPO are determined mainly by the occupied orbitals O 2p and Cs 5p as well as by the unoccupied orbitals Cs 5d and Li 2p. For the SHG response of a material, the polarizable atomic orbitals of the occupied and the unoccupied states are both important.}, number={15}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Cheng, Xiyue and Whangbo, Myung-Hwan and Guo, Guo-Cong and Hong, Maochun and Deng, Shuiquan}, year={2018}, month={Apr}, pages={3933–3937} }
 @article{lu_mentre_gordon_whangbo_wattiaux_duttine_tiercelin_kabbour_2017, title={A comprehensive study of magnetic exchanges in the layered oxychalcogenides Sr(3)Fe(2)O(5)Cu(2)Q(2) (Q = S, Se)}, volume={444}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2017.07.026}, abstractNote={The layered oxysulfide Sr3Fe2O5Cu2S2 was prepared, and its crystal structure and magnetic properties were characterized by synchrotron X-ray diffraction (XRD), powder neutron diffraction (PND), Mössbauer spectroscopy measurements and by density functional theory (DFT) calculations. In addition, the spin exchange interactions leading to the ordered magnetic structure of Sr3Fe2O5Cu2S2 were compared with those of its selenium analogue Sr3Fe2O5Cu2Se2. The oxysulfide Sr3Fe2O5Cu2S2 adopts a G-type antiferromagnetic (AFM) structure at a temperature in the range 485–512 K, which is comparable with the three-dimensional (3D) AFM ordering temperature, TN ≈ 490 K, found for Sr3Fe2O5Cu2Se2. Consistent with this observation, the spin exchange interactions of the magnetic (Sr3Fe2O5)2+ layers are slightly greater (but comparable) for oxysulfide than for the oxyselenide. Attempts to reduce or oxidize Sr3Fe2O5Cu2S2 using topochemical routes yield metallic Fe.}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Lu, Minfeng and Mentre, Olivier and Gordon, Elijah E. and Whangbo, Myung-Hwan and Wattiaux, Alain and Duttine, Mathieu and Tiercelin, Nicolas and Kabbour, Houria}, year={2017}, month={Dec}, pages={147–153} }
 @article{xu_an_liu_qin_zhang_dai_wang_wang_whangbo_huang_2017, title={Enhancing the photocatalytic activity of BiOX (X = Cl, Br, and I), (BiO)(2)CO3 and Bi2O3 by modifying their surfaces with polar organic anions, 4-substituted thiophenolates}, volume={5}, ISSN={["2050-7496"]}, DOI={10.1039/c7ta03970k}, abstractNote={Bi-based semiconductors surface-modified by polar organic molecules display extended visible light absorption and enhanced photocatalytic activity.}, number={27}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Xu, Benyan and An, Yang and Liu, Yuanyuan and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Wang, Zeyan and Wang, Peng and Whangbo, Myung-Hwan and Huang, Baibiao}, year={2017}, month={Jul}, pages={14406–14414} }
 @article{barroux_jiang_paul_massuyeau_geois_gordon_whangbo_jobic_gautier_2017, title={Fine-Tuning the Properties of Doped Multifunctional Materials by Controlled Reduction of Dopants}, volume={23}, ISSN={["1521-3765"]}, DOI={10.1002/chem.201605707}, abstractNote={Abstract The physical properties of doped multifunctional compounds are commonly tuned by controlling the amount of dopants, but this control is limited because all the properties are influenced simultaneously by this single parameter. Here, we present a strategy that enables the fine‐tuning of a specific combination of properties by controlling the reduction of dopants. The feasibility of this approach was demonstrated by optimizing the near‐IR photoluminescence of strontium titanate SrTiO 3 :Ni for potential applications in biomedicine for a range of absorbance in the visible/near‐IR region. We discussed how material properties, such as luminescence, conductivity, or photocatalytic properties can be designed by carefully controlling the ratio of dopants in different oxidation states.}, number={13}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Barroux, Hugo and Jiang, Tengfei and Paul, Camille and Massuyeau, Florian and Geois, Romain and Gordon, Elijah E. and Whangbo, Myung-Hwan and Jobic, Stephane and Gautier, Romain}, year={2017}, month={Mar}, pages={2998–3001} }
 @article{gordon_koo_deng_koehler_whangbo_2017, title={Group of Quantum Bits Acting as a Bit Using a Single-Domain Ferromagnet of Uniaxial Magnetic Ions}, volume={18}, ISSN={["1439-7641"]}, DOI={10.1002/cphc.201700609}, abstractNote={Abstract Read/write operations with individual quantum bits (i.e., qbits) are a challenging problem to solve in quantum computing. To alleviate this difficulty, we considered the possibility of using a group of qbits that act collectively as a bit (hereafter, a group bit or a gbit, in short). A promising candidate for a gbit is a single‐domain ferromagnet (SDF) independent of its size, which can be prepared as a magnet of well‐separated uniaxial magnetic ions (UMIs) at sites of no electric dipole moment with their uniaxial axes aligned along one common direction. When magnetized, the UMIs of such a magnet have a ferromagnetic (FM) arrangement and the resulting SDF becomes a gbit with its two opposite moment orientations representing the |0⟩ and |1⟩ states of a bit. We probed the requirements for such magnets and identified several 2H‐perovskites as materials satisfying these requirements.}, number={16}, journal={CHEMPHYSCHEM}, author={Gordon, Elijah E. and Koo, Hyun-Joo and Deng, Shuiquan and Koehler, Juergen and Whangbo, Myung-Hwan}, year={2017}, month={Aug}, pages={2147–2150} }
 @article{clune_hughey_lee_abhyankar_ding_dalal_whangbo_singleton_musfeldt_2017, title={Magnetic field-temperature phase diagram of multiferroic [(CH3)(2)NH2]Mn(HCOO)(3)}, volume={96}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.96.104424}, abstractNote={We combined pulsed field magnetization and first-principles spin-density calculations to reveal the magnetic field-temperature phase diagram and spin state character in multiferroic $[{({\mathrm{CH}}_{3})}_{2}{\mathrm{NH}}_{2}]\mathrm{Mn}{(\mathrm{HCOO})}_{3}$. Despite similarities with the rare earth manganites, the phase diagram is analogous to other Mn-based quantum magnets with a 0.31 T spin flop, a 15.3 T transition to the fully polarized state, and short-range correlations that persist above the ordering temperature. The experimentally accessible saturation field opens the door to exploration of the high-field phase.}, number={10}, journal={PHYSICAL REVIEW B}, author={Clune, A. J. and Hughey, K. D. and Lee, C. and Abhyankar, N. and Ding, X. and Dalal, N. S. and Whangbo, M. -H. and Singleton, J. and Musfeldt, J. L.}, year={2017}, month={Sep} }
 @article{al-wahish_o'neal_lee_fan_hughey_yokosuk_clune_li_schlueter_manson_et al._2017, title={Magnetic phase transitions and magnetoelastic coupling in S=1/2 Heisenberg antiferromagnets}, volume={95}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.95.104437}, abstractNote={We combined magneto-infrared spectroscopy and first-principles calculations to unravel the role of spin-phonon coupling in the vicinity of the magnetic field-driven phase transitions in two chemically similar $S=1/2$ Heisenberg antiferromagnets, ${\mathrm{CuF}}_{2}({\mathrm{H}}_{2}\mathrm{O}){}_{2}$(3-Clpy) and $[\mathrm{Cu}{(\mathrm{pyz})}_{2}({\mathrm{HF}}_{2})]{\mathrm{PF}}_{6}$. This comparison resolves questions about the conditions under which the lattice participates in magnetic-field-driven transitions and, at the same time, provides a way to predict how the lattice is likely to support microscopic spin rearrangements.}, number={10}, journal={PHYSICAL REVIEW B}, author={al-Wahish, Amal and O'Neal, K. R. and Lee, C. and Fan, S. and Hughey, K. and Yokosuk, M. O. and Clune, A. J. and Li, Z. and Schlueter, J. A. and Manson, J. L. and et al.}, year={2017}, month={Mar} }
 @article{bussmann-holder_koehler_simon_whangbo_bianconi_2017, title={Multigap Superconductivity at Extremely High Temperature: A Model for the Case of Pressurized H2S}, volume={30}, ISSN={["1557-1947"]}, DOI={10.1007/s10948-016-3947-7}, abstractNote={It is known that in pressurized H2S the complex electronic structure in the energy range of 200 meV near the chemical potential can be separated into two electronic components, the first characterized by steep bands with a high Fermi velocity and the second by flat bands with a vanishing Fermi velocity. Also the phonon modes interacting with electrons at the Fermi energy can be separated into two components: hard modes with high energy around 150 meV and soft modes with energies around 60 meV. Therefore we discuss here a multiband scenario in the standard BCS approximation where the effective BCS coupling coefficient is in the range 0.1- 0.32. We consider a first (second) BCS condensate in the strong (weak) coupling regime 0.32 (0.15). We discuss different scenario segregated in different portions of the material. The results show the phenomenology of unconventional superconducting phases in this two-gap superconductivity scenario where there are two electronic components in two Fermi surface spots, the pairing is mediated by either by a soft or a hard phonon branch where the inter-band exchange term, also if small, plays a key role for the emergence of high temperature superconductivity in pressurized sulfur hydride.}, number={1}, journal={JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM}, author={Bussmann-Holder, A. and Koehler, J. and Simon, A. and Whangbo, M. and Bianconi, A.}, year={2017}, month={Jan}, pages={151–156} }
 @article{behrh_isobe_massuyeau_serier-brault_gordon_koo_whangbo_gautier_jobic_2017, title={Oxygen-Vacancy-Induced Midgap States Responsible for the Fluorescence and the Long-Lasting Phosphorescence of the Inverse Spinel Mg(Mg,Sn)O-4}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b03906}, abstractNote={Samples of inverse spinel Mg2SnO4 were prepared using a ceramic method, their phosphorescence phenomenon was probed by optical measurements, and its cause was explored on the basis of density functional theory calculations for model structures of Mg2SnO4 with oxygen vacancies VO. Mg2SnO4 exhibits long-lasting luminescence at two different wavelength regions, peaking at ∼498 and ∼755 nm. A Sn-VO-Sn defect plus a Mg vacancy VMg away from the VO generates the empty midgap states, σSn-Sn and σSn-Sn*, localized at the Sn-VO-Sn defect, while an oxygen vacancy VO between adjacent Sn4+ and Mg2+ sites creates a filled midgap state Sn2+ (5s2 lone pair) lying below the σSn-Sn level. The long-lasting luminescence at two different wavelength regions and the up-conversion photostimulated luminescence observed for undoped Mg2SnO4 are well explained by considering the σSn-Sn* level as the trapping level for a photogenerated electron.}, number={3}, journal={CHEMISTRY OF MATERIALS}, author={Behrh, Gaganpreet Kaur and Isobe, Masahiko and Massuyeau, Florian and Serier-Brault, Helene and Gordon, Elijah E. and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Gautier, Romain and Jobic, Stephane}, year={2017}, month={Feb}, pages={1069–1075} }
 @article{jiang_liang_zheng_liu_wang_wang_zhang_qin_dai_whangbo_et al._2017, title={Photocatalytic reduction of CO2 to methanol by three-dimensional hollow structures of Bi2WO6 quantum dots}, volume={219}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2017.07.023}, abstractNote={Three-dimensional hollow structures made up of Bi2WO6 quantum dots were prepared by one-pot solvothermal synthesis using ethylene glycol as reactive solvent. The structural, optical and CO2-photoreduction to methanol of these hollow structures were investigated. The ethylene glycol is important not only in assembling the three-dimensional hollow structures but also in suppressing the agglomeration of Bi2WO6 quantum dots. The hollow structure of Bi2WO6 quantum dots has a much higher CO2 adsorption capacity and a wider band gap than does bulk-Bi2WO6, so that the CO2 photoconversion reaction is much faster for the hollow structures made up of Bi2WO6 quantum dots.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Jiang, Zaiyong and Liang, Xizhuang and Zheng, Hailong and Liu, Yuanyuan and Wang, Zeyan and Wang, Peng and Zhang, Xiaoyang and Qin, Xiaoyan and Dai, Ying and Whangbo, Myung-Hwan and et al.}, year={2017}, month={Dec}, pages={209–215} }
 @article{xu_mace_enriquez_bao_harrell_chen_whangbo_2017, title={Roles of reaction kinetics of CO2 on a PrBaCo2O5.5+delta surfaces}, volume={7}, ISSN={["2046-2069"]}, DOI={10.1039/c7ra06362h}, abstractNote={A symmetric PBCO/YSZ/PBCO cell (where PBCO refers to PrBaCo<sub>2</sub>O<sub>5.5+δ</sub>, and YSZ to yttria stabilized zirconia) was designed and fabricated for the investigation of the catalytic nature and reaction kinetics of CO<sub>2</sub> on PBCO surfaces.}, number={64}, journal={RSC ADVANCES}, author={Xu, Xing and Mace, Brennan and Enriquez, Erik and Bao, Shanyong and Harrell, Zach and Chen, Chonglin and Whangbo, Myung-Hwan}, year={2017}, pages={40558–40562} }
 @article{lee_an_gordon_ji_park_shim_lim_whangbo_2017, title={Seebeck Coefficients of Layered BiCuSeO Phases: Analysis of Their Hole-Density Dependence and Quantum Confinement Effect}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.7b00028}, abstractNote={Hole-doped layered BiCuSeO phases include substitutionally doped Bi1–xAxCuSeO (A = alkali, alkaline earth) as well as vacancy-doped Bi1−δCu1-γSeO and Bi1−δCuSeO. To probe how their Seebeck coefficients are related to their hole density p, we calculated the Seebeck coefficient for defect-free BiCuSeO as a function of the hole density, which is generated by lowering the Fermi level from the valence band maximum (VBM). In addition, we calculated the Seebeck coefficient for Bi1−δCuSeO (δ = 1/32, 1/16) with a large number of Bi vacancies. The Seebeck coefficients of the hole-doped BiCuSeO phases are governed by the electronic states lying within ∼0.5 eV from the VBM. These states are composed of largely Cu 3d xz/yz and Se 4p x/y states and possess the character of a uniform one-dimensional (1D) chain rather than a uniform two-dimensional (2D) lattice expected for a layered phase. The observed S-vs-p relationship for Bi1–xAxCuSeO (A = alkali, alkaline earth) as well as Bi1−δCu1-γSeO (δ = 0, 0.025; γ = 0, 0.025) and Bi1−δCuSeO (δ = 0.0, 0.025) is very well reproduced by the calculated relationship for defect-free BiCuSeO within the rigid band approximation. The observed S-vs-p relationship reflects the quantum confinement effect of uniform 1D chains, despite that the hole-doped BiCuSeO phases consist of 2D layers, (Cu2Se2)2– and (Bi2O2)2+. The drastic decrease in the S values of Bi1−δCuSeO with large δ (= 0.05, 0.075, 0.10) arises from the loss of the quantum confinement effect in the (Cu2Se2)2– layers; that is, the uniform 1D chain character is lost because of their geometry distortion induced by a large number of Bi vacancies.}, number={5}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and An, Tae-Ho and Gordon, Elijah E. and Ji, Hyo Seok and Park, Chan and Shim, Ji-Hoon and Lim, Young Soo and Whangbo, Myung-Hwan}, year={2017}, month={Mar}, pages={2348–2354} }
 @article{koo_gordon_whangbo_2017, title={Single-Domain Ferromagnet of Noncentrosymmetric Uniaxial Magnetic Ions and Magnetoelectric Interaction}, volume={56}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201701699}, abstractNote={The feasibility of a single-domain ferromagnet based on uniaxial magnetic ions was examined. For a noncentrosymmetric uniaxial magnetic ion of magnetic moment μ at a site of local electric dipole moment p, it is unknown to date whether μ prefers to be parallel or antiparallel to μ. The nature of this magnetoelectric interaction was probed in terms of analogical reasoning based on the Rashba effect and density functional theory (DFT) calculations. We show that μ and p prefer an antiparallel arrangement, predict that Fe-doped CaZnOS is a single-domain ferromagnet like a bar magnet, and find the probable cause for the ferromagnetism and weak magnetization hysteresis in Fe-doped hexagonal ZnO and ZnS at very low dopant concentrations.}, number={34}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Koo, Hyun-Joo and Gordon, Elijah E. and Whangbo, Myung-Hwan}, year={2017}, month={Aug}, pages={10196–10199} }
 @article{golubev_dinnebier_schulz_kremer_langbein_senyshyn_law_hansen_koo_whangbo_2017, title={Structural and Magnetic Properties of the Trirutile-type 1D-Heisenberg Anti-Ferromagnet CuTa2O6}, volume={56}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.7b00421}, abstractNote={We prepared trirutile-type polycrystalline samples of CuTa2O6 by low-temperature decomposition of a Cu-Ta-oxalate precursor. Diffraction studies at room temperature identified a slight monoclinic distortion of the hitherto surmised tetragonal trirutile crystal structure. Detailed high-temperature X-ray and neutron powder diffraction investigations as well as Raman scattering spectroscopy revealed a structural phase transition at 503(3) K from the monoclinic structure to the tetragonal trirutile structure. GGA+U density functional calculations of the spin-exchange parameters as well as magnetic susceptibility and isothermal magnetization measurements reveal that CuTa2O6 is a new 1D Heisenberg magnet with predominant anti-ferromagnetic nearest-neighbor intrachain spin-exchange interaction of ∼50 K. Interchain exchange is a factor of ∼5 smaller. Heat capacity and low-temperature high-intensity neutron powder diffraction studies could not detect long-range order down to 0.45 K.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Golubev, Aleksandr and Dinnebier, Robert E. and Schulz, Armin and Kremer, Reinhard K. and Langbein, Hubert and Senyshyn, Anatoliy and Law, Joseph M. and Hansen, Thomas C. and Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2017}, month={Jun}, pages={6318–6329} }
 @article{cheng_gordon_whangbo_deng_2017, title={Superconductivity Induced by Oxygen Doping in Y2O2Bi}, volume={56}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201701427}, abstractNote={Abstract When doped with oxygen, the layered Y 2 O 2 Bi phase becomes a superconductor. This finding raises questions about the sites for doped oxygen, the mechanism of superconductivity, and practical guidelines for discovering new superconductors. We probed these questions in terms of first‐principles calculations for undoped and O‐doped Y 2 O 2 Bi. The preferred sites for doped O atoms are the centers of Bi 4 squares in the Bi square net. Several Bi 6p x / y bands of Y 2 O 2 Bi are raised in energy by oxygen doping because the 2p x / y orbitals of the doped oxygen make antibonding possible with the 6p x / y orbitals of surrounding Bi atoms. Consequently, the condition necessary for the “flat/steep” band model for superconductivity is satisfied in O‐doped Y 2 O 2 Bi.}, number={34}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Cheng, Xiyue and Gordon, Elijah E. and Whangbo, Myung-Hwan and Deng, Shuiquan}, year={2017}, month={Aug}, pages={10123–10126} }
 @article{xu_an_liu_huang_qin_zhang_dai_whangbo_2016, title={An efficient visible-light photocatalyst made from a nonpolar layered semiconductor by grafting electron-withdrawing organic molecules to its surface}, volume={52}, ISSN={["1364-548X"]}, DOI={10.1039/c6cc07849d}, abstractNote={The UV-light responsive Bi<sub>2</sub>O<sub>2</sub>(HCOO)<sub>2</sub> (BFM) becomes an efficient visible-light photocatalyst when it is chemically modified with 4-substituted electron-withdrawing thiophenolates <sup>−</sup>S-C<sub>6</sub>H<sub>4</sub>Z.}, number={92}, journal={CHEMICAL COMMUNICATIONS}, author={Xu, Benyan and An, Yang and Liu, Yuanyuan and Huang, Baibiao and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2016}, pages={13507–13510} }
 @misc{stroppa_barone_di sante_cuoco_picozzi_whangbo_2016, title={Analogies between Jahn-Teller and Rashba spin physics}, volume={116}, ISSN={["1097-461X"]}, DOI={10.1002/qua.25209}, abstractNote={In developing physical theories, analogical reasoning has been found to be very powerful, as attested by a number of important historical examples. An analogy between two apparently different phenomena, once established, allows one to transfer information and bring new concepts from one phenomenon to the other. Here, we discuss an important analogy between two widely different physical problems, namely, the Jahn–Teller distortion in molecular physics and the Rashba spin splitting in condensed matter physics. By exploring their conceptual and mathematical features and by searching for the counterparts between them, we examine the orbital texture in Jahn–Teller systems, as the counterpart of the spin texture of the Rashba physics, and put forward a possible way of experimentally detecting the orbital texture. Finally, we discuss the analogy by comparing the coexistence of linear Rashba + Dresselhaus effects and Jahn–Teller problems for specific symmetries, which allow for nontrivial spin and orbital textures, respectively.}, number={20}, journal={INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY}, author={Stroppa, Alessandro and Barone, Paolo and Di Sante, Domenico and Cuoco, Mario and Picozzi, Silvia and Whangbo, Myung-Hwan}, year={2016}, month={Oct}, pages={1442–1450} }
 @article{kovrugin_gordon_kasapbasi_whangbo_colmont_siidra_colis_krivovichev_mentre_2016, title={Bonding Scheme, Hydride Character, and Magnetic Paths of (HPO3)(2-) Versus (SeO3)(2-) Building Units in Solids}, volume={120}, ISSN={["1932-7447"]}, DOI={10.1021/acs.jpcc.5b10889}, abstractNote={The abilities of the (HPO3)2– and (SeO3)2– anions as structure building units and as spin exchange paths between magnetic ions were investigated by preparing and analyzing the isostructural Fe2(SeO3)3 and Fe2(HPO3)3. In both compounds, the face-sharing Fe2O9 dimers are interconnected into chains by the (HPO3)2– and (SeO3)2– anions. The (HPO3)2– is the structural counterpart of the Se electron lone pair of (SeO3)2– due to the weak hydride character of the terminal hydrogen. However, they differ considerably as spin exchange paths between magnetic cations. Both compounds exhibit an effective magnetic dimer behavior, unexpectedly arising from the interdimer Fe—O···O—Fe exchange along the chain, but weaker in Fe2(HPO3)3 by a factor of ∼3. It is consistent with the general tendencies of the phosphite anions to act as a weak magnetic mediator, which is caused by the through-bond effect of the P3+ ion in the Fe—O···P3+···O—Fe exchange path, much weaker than in the selenite phase in absence of P3+d contribution. Reasons for stronger exchanges through phosphates or sulfates are also discussed.}, number={3}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kovrugin, Vadim M. and Gordon, Elijah E. and Kasapbasi, Esra E. and Whangbo, Myung-Hwan and Colmont, Marie and Siidra, Oleg I. and Colis, Silviu and Krivovichev, Sergey V. and Mentre, Olivier}, year={2016}, month={Jan}, pages={1650–1656} }
 @article{caslin_kremer_razavi_hanfland_syassen_gordon_whangbo_2016, title={Competing Jahn-Teller distortions and hydrostatic pressure effects in the quasi-one-dimensional quantum ferromagnet CuAs2O4}, volume={93}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.93.022301}, abstractNote={${\mathrm{CuAs}}_{2}{\mathrm{O}}_{4}$ is a $S=1/2$ quasi-one-dimensional ribbon chain compound which orders ferromagnetically at 7.4 K under ambient conditions. ${\mathrm{CuAs}}_{2}{\mathrm{O}}_{4}$ features nearest- and next-nearest-neighbor spin-exchange interactions along the spin chains with a ratio $\ensuremath{\alpha}={J}_{\mathrm{nn}}/{J}_{\mathrm{nnn}}$ in close proximity to the quantum critical point at $\ensuremath{\alpha}=\ensuremath{-}4$. We apply hydrostatic pressure up to $\ensuremath{\sim}11.5$ GPa and examine the structural and magnetic properties using Raman spectroscopy, single-crystal synchrotron x-ray diffraction, and magnetic susceptibility measurements. External pressure severely reduces the axial Jahn-Teller elongations of the oxygen octahedra surrounding the ${\mathrm{Cu}}^{2+}$ cations and stabilizes the ferromagnetic ground state. At 9.2(2) GPa, we detect a structural phase transition leading to an increased twisting of the ${\mathrm{CuO}}_{2}$ ribbon chains and a large drop of the magnetic ordering temperature. Ab initio density functional theory calculations of the spin-exchange parameters, using the structural parameters as a function of pressure, support the experimental findings.}, number={2}, journal={PHYSICAL REVIEW B}, author={Caslin, K. and Kremer, R. K. and Razavi, F. S. and Hanfland, M. and Syassen, K. and Gordon, E. E. and Whangbo, M. -H.}, year={2016}, month={Jan} }
 @article{gordon_kohler_whangbo_2016, title={Condensed-matter equation of states covering a wide region of pressure studied experimentally}, volume={6}, journal={Scientific Reports}, author={Gordon, E. E. and Kohler, J. and Whangbo, M. H.}, year={2016} }
 @article{jiang_liu_jing_huang_zhang_qin_dai_whangbo_2016, title={Enhancing the Photocatalytic Activity of BiVO4 for Oxygen Evolution by Ce Doping: Ce3+ Ions as Hole Traps}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.5b10856}, abstractNote={To enhance the photocatalytic activity of monoclinic BiVO4 for O2 evolution from water, Ce-doped BiVO4 was prepared using the one-pot facile solvothermal method and characterized via XRD, Raman, XPS, and electrochemical impedance spectroscopy (EIS). The XPS spectra confirm that Ce component is Ce3+ ions instead of Ce4+ ions. From the structural characterization and the calculations of formation energies it has been stated that the doping of Ce3+ ions takes place at Bi3+ sites without changing the host structure. The as-prepared Ce-doped BiVO4 samples display significantly enhanced photocatalytic O2 evolution activities from water compared to pristine BiVO4. Density of states calculations indicate that Ce3+ ions act as hole traps, thereby delaying the recombination of photogenerated electrons and holes. The results demonstrate that the substitution of the remaining monoclinic crystal structure may offer an attractive alternative approach for the doping of BiVO4 to enhance the evolution activity of photocatalytic O2.}, number={4}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Jiang, Zaiyong and Liu, Yuanyuan and Jing, Tao and Huang, Baibiao and Zhang, Xiaoyang and Qin, Xiaoyan and Dai, Ying and Whangbo, Myung-Hwan}, year={2016}, month={Feb}, pages={2058–2063} }
 @article{lee_hong_son_kan_shim_whangbo_2016, title={Magnetic structure of (C5H12N)CuBr3: origin of the uniform Heisenberg chain behavior and the magnetic anisotropy of the Cu2+ (S=1/2) ions}, volume={6}, ISSN={["2046-2069"]}, DOI={10.1039/c5ra26341g}, abstractNote={The AFM chain behavior observed for (pipH)CuBr<sub>3</sub>is not caused by the CuBr<sub>3</sub>chains, but by the interchain exchanges leading to two-leg spin ladders. The Cu<sup>2+</sup>ions have easy-axis anisotropy, and this arises largely from the SOC of the Br<sup>−</sup>ligands.}, number={27}, journal={RSC ADVANCES}, author={Lee, Changhoon and Hong, Jisook and Son, Won-joon and Kan, Erjun and Shim, Ji Hoon and Whangbo, Myung-Hwan}, year={2016}, pages={22722–22727} }
 @article{bruyer_di sante_barone_stroppa_whangbo_picozzi_2016, title={Possibility of combining ferroelectricity and Rashba-like spin splitting in monolayers of the 1T-type transition-metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te)}, volume={94}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.94.195402}, abstractNote={First-principles calculations were carried out to explore the possible coupling between spin-polarized electronic states and ferroelectric polarization in monolayers of transition-metal dichalcogenides $M{X}_{2}$ ($M=\mathrm{Mo},\mathrm{W};X=\mathrm{S},\mathrm{Se},\mathrm{Te})$ with distorted octahedrally coordinated $1T$ structures. For ${d}^{2}$ metal ions, two competing metal clustering effects can take place, where metal ions are arranged in trimers or zigzag chains. Among these, the former structural distortion comes along with an improper ferroelectric phase which persists in the monolayer limit. Switchable Rashba-like spin-polarization features are predicted in the trimerized polytype, which can be permanently tuned by acting on its ferroelectric properties. The polar trimerized structure is found to be stable for $1T\ensuremath{-}{\mathrm{MoS}}_{2}$ only, while the nonpolar polytype with zigzag metal clustering is predicted to stabilize for other transition-metal dichalcogenides with ${d}^{2}$ metal ions.}, number={19}, journal={PHYSICAL REVIEW B}, author={Bruyer, Emilie and Di Sante, Domenico and Barone, Paolo and Stroppa, Alessandro and Whangbo, Myung-Hwan and Picozzi, Silvia}, year={2016}, month={Nov} }
 @article{gordon_xiang_kohler_whangbo_2016, title={Spin orientations of the spin-half Ir4+ ions in Sr3NiIrO6, Sr2IrO4, and Na2IrO3: Density functional, perturbation theory, and Madelung potential analyses}, volume={144}, number={11}, journal={Journal of Chemical Physics}, author={Gordon, E. E. and Xiang, H. J. and Kohler, J. and Whangbo, M. H.}, year={2016} }
 @article{kenneth r. o'neal_holinsworth_chen_peterson_carreiro_lee_manson_whangbo_li_liu_et al._2016, title={Spin-Lattice Coupling in [Ni(HF2)(pyrazine)(2)]SbF6 Involving the HF2- Superexchange Pathway}, volume={55}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.6b01679}, abstractNote={Magnetoelastic coupling in the quantum magnet [Ni(HF2)(pyrazine)2]SbF6 has been investigated via vibrational spectroscopy using temperature, magnetic field, and pressure as tuning parameters. While pyrazine is known to be a malleable magnetic superexchange ligand, we find that HF2– is surprisingly sensitive to external stimuli and is actively involved in both the magnetic quantum phase transition and the series of pressure-induced structural distortions. The amplified spin–lattice interactions involving the bifluoride ligand can be understood in terms of the relative importance of the intra- and interplanar magnetic energy scales.}, number={23}, journal={INORGANIC CHEMISTRY}, author={Kenneth R. O'Neal and Holinsworth, Brian S. and Chen, Zhiguo and Peterson, Peter K. and Carreiro, Kimberly E. and Lee, Changhoon and Manson, Jamie L. and Whangbo, Myung-Hwan and Li, Zhigiang and Liu, Zhenxian and et al.}, year={2016}, month={Dec}, pages={12172–12178} }
 @article{gordon_xu_xiang_bussmann-holder_kremer_simon_koehler_whangbo_2016, title={Structure and Composition of the 200K-Superconducting Phase of H2S at Ultrahigh Pressure: The Perovskite (SH-)(H3S+)}, volume={55}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201511347}, abstractNote={H2S is converted under ultrahigh pressure (> 110 GPa) to a metallic phase that becomes superconducting with a record Tc of 200 K. It has been proposed that the superconducting phase is body-centered cubic H3S ( Im3m , a = 3.089 {\AA}) resulting from a decomposition reaction 3H2S --> 2H3S + S. The analogy of H2S and H2O leads us to a very different conclusion. The well-known dissociation of water into H3O+ and OH- increases by orders of magnitude under pressure. An equivalent behavior of H2S is anticipated under pressure with the dissociation, 2H2S --> H3S+ + SH- forming a perovskite structure (SH-)(H3S+), which consists of corner-sharing SH6 octahedra with SH- at each A-site (i.e., the center of each S8 cube). Our DFT calculations show that the perovskite (SH-)(H3S+) is thermodynamically more stable than the Im3m structure of H3S, and suggest that the A-site H atoms are most likely fluxional even at Tc.}, number={11}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Gordon, Elijah E. and Xu, Ke and Xiang, Hongjun and Bussmann-Holder, Annette and Kremer, Reinhard K. and Simon, Arndt and Koehler, Juergen and Whangbo, Myung-Hwan}, year={2016}, month={Mar}, pages={3682–3684} }
 @article{bao_xu_enriquez_mace_chen_kelliher_chen_zhang_whangbo_dong_et al._2015, title={Atomically layer-by-layer diffusion of oxygen/hydrogen in highly epitaxial PrBaCo2O5.5+delta thin films}, volume={107}, number={24}, journal={Applied Physics Letters}, author={Bao, S. Y. and Xu, X. and Enriquez, E. and Mace, B. E. and Chen, G. and Kelliher, S. P. and Chen, C. L. and Zhang, Y. M. and Whangbo, M. H. and Dong, C. and et al.}, year={2015} }
 @article{enriquez_xu_bao_harrell_chen_choi_jun_kim_whangbo_2015, title={Catalytic Dynamics and Oxygen Diffusion in Doped PrBaCo2O5.5+delta Thin Films}, volume={7}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.5b07688}, abstractNote={The Sr and Fe codoped double perovskites PrBaCo2O5.5+δ (PrBCO) thin films of Pr(Ba0.5Sr0.5)(Co1.5Fe0.5)O5.5+δ (PBSCFO) were epitaxially grown for chemical catalytic studies. The resistance behavior of PBSCFO epitaxial films was monitored under the switching flow of reducing and oxidizing gases as a function of the gas flow time, t, using an electrical conductivity relaxation (ECR) experimental setup. The R(t) vs t relationships determined at various temperatures show the occurrence of two oxidation processes, Co(2+)/Co(3+) ↔ Co(3+) and Co(3+) ↔ Co(3+)/Co(4+). Mathematical fitting of the observed R(t) vs t relationships was carried out using Fick's second law for one-dimensional diffusion of charge carriers to derive the diffusivity D(T) and τ(T) for the two processes at various temperatures, T. The D(T) vs T relationships were analyzed in terms of the Arrhenius relationship to find the activation energies Ea for each process. Oscillations in the dR(t)/dt plots, observed under oxidation reactions, were discussed in terms of a layer-by-layer oxygen vacancy exchange diffusion mechanism. Our work suggests that thin films of LnBCO (Ln = lanthanide) with their A and B sites doped as in PBSCFO are excellent candidates for the development of low or intermediate temperature energy conversion devices and gas sensor applications.}, number={43}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Enriquez, Erik and Xu, Xing and Bao, Shanyong and Harrell, Zach and Chen, Chonglin and Choi, Sihyuk and Jun, Areum and Kim, Guntae and Whangbo, Myung-Hwan}, year={2015}, month={Nov}, pages={24353–24359} }
 @article{zvereva_presniakov_whangbo_koo_frantsuzenko_savelieva_sobolev_nalbandyan_shih_chiang_et al._2015, title={Crucial Role of Site Disorder and Frustration in Unusual Magnetic Properties of Quasi-2D Triangular Lattice Antimonate Na4FeSbO6}, volume={46}, ISSN={["1613-7507"]}, DOI={10.1007/s00723-015-0700-5}, number={10}, journal={APPLIED MAGNETIC RESONANCE}, author={Zvereva, Elena A. and Presniakov, Igor A. and Whangbo, Myung-Hwan and Koo, Hyun-Joo and Frantsuzenko, Tatyana V. and Savelieva, Olga A. and Sobolev, Alexey V. and Nalbandyan, Vladimir B. and Shih, Pei-Shan and Chiang, Jen-Che and et al.}, year={2015}, month={Oct}, pages={1121–1145} }
 @article{wei_dai_huang_li_naegele_over_whangbo_jacob_2015, title={Density Functional Characterization of the Electronic Structures and Band Bending of Rutile RuO2/TiO2(110) Heterostructures}, volume={119}, ISSN={["1932-7447"]}, DOI={10.1021/acs.jpcc.5b01884}, abstractNote={The enhanced catalytic and photocatalytic activities of a RuO2 layer deposited on the TiO2(110) surface were examined by constructing model RuO2/TiO2(110) heterostructures with and without oxygen vacancies and performing density functional calculations. The formation of the heterojunction only weakly affects the atomic structure of the interface due to a pseudomorphic deposition but causes a strong electron density accumulation in the interface as well as a bending of the valence and conduction bands of TiO2. The electron accumulation in the interface creates a strong internal electric field, which helps to effectively separate photogenerated electron–hole pairs during a photocatalytic process. Finally, we report on the catalytic role of oxygen vacancies at the surface.}, number={22}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Wei, Wei and Dai, Ying and Huang, Baibiao and Li, Xiaoke and Naegele, Florian and Over, Herbert and Whangbo, Myung-Hwan and Jacob, Timo}, year={2015}, month={Jun}, pages={12394–12399} }
 @article{di sante_stroppa_barone_whangbo_picozzi_2015, title={Emergence of ferroelectricity and spin-valley properties in two-dimensional honeycomb binary compounds}, volume={91}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.91.161401}, abstractNote={First-principles calculations presented in this Rapid Communication suggest that a number of $A\phantom{\rule{0}{0ex}}B$ binary honeycomb monolayers should be ferroelectric. Dipoles arise from the buckled structure, and the polarization reversal occurs via switching the structural buckling which can be triggered by an external electric field. The authors address the emerging valley-dependent properties arising from the ferroelectric bistability and explore the intimate link between ferroelectricity, spin-valley physics, and Rashba spin-splitting phenomena.}, number={16}, journal={PHYSICAL REVIEW B}, author={Di Sante, Domenico and Stroppa, Alessandro and Barone, Paolo and Whangbo, Myung-Hwan and Picozzi, Silvia}, year={2015}, month={Apr} }
 @article{li_jing_liu_huang_dai_zhang_qin_whangbo_2015, title={Enhancing the Efficiency of Water Oxidation by Boron-Doped BiVO4 under Visible Light: Hole Trapping by BO4 Tetrahedra}, volume={80}, ISSN={["2192-6506"]}, DOI={10.1002/cplu.201500110}, abstractNote={Abstract Boron‐doped monoclinic and tetragonal phases of BiVO 4 were prepared by using the urea precipitation method, and the visible‐light photocatalytic activities of pristine and boron‐doped BiVO 4 for oxygen generation from water were compared. Boron doping enhances the photocatalytic activities of BiVO 4 . The reasons for this enhancement were probed by performing X‐ray photoelectron, Raman, and electrochemical impedance spectroscopy measurements, and also by performing density functional calculations for model boron‐doped BiVO 4 structures. The photocatalytic activities of BiVO 4 is enhanced by boron doping because the resulting BO 4 tetrahedra, which are smaller than the VO 4 tetrahedra, create an occupied defect level per boron lying approximately 0.17 eV above the valence‐band maximum of pristine BiVO 4 , and this defect level is localized because it is made up of the O 2 p levels of the BO 4 tetrahedron. Thus, the BO 4 tetrahedra that result from boron doping act as hole traps, thereby slowing down the recombination of photogenerated electrons and holes.}, number={7}, journal={CHEMPLUSCHEM}, author={Li, Yanqing and Jing, Tao and Liu, Yuanyuan and Huang, Baibiao and Dai, Ying and Zhang, Xiaoyang and Qin, Xiaoyan and Whangbo, Myung-Hwan}, year={2015}, month={Jul}, pages={1113–1118} }
 @article{ma_dai_wei_huang_whangbo_2015, title={Insights into How Fluorine-Adsorption and n-Type Doping Affect the Relative Stability of the (001) and (101) Surfaces of TiO2: Enhancing the Exposure of More Active but Thermodynamically Less Stable (001)}, volume={6}, ISSN={["1948-7185"]}, DOI={10.1021/acs.jpclett.5b00595}, abstractNote={The stability of both the pure and fluorine (F)-adsorbed surface of TiO2 is examined on the basis of density functional calculations. For pure surfaces, both the beneficial local geometric structures and local potential strengthen the Ti-O binding in (101), rendering it the most stable surface. For F-adsorbed surfaces, F-adsorption significantly weakens the Ti-O bonds in (101) but strengthens them in (001), so that (001) becomes more stable than (101) for the F-adsorbed surfaces. On the basis of this observation, we further show that the n-type doping in TiO2 can significantly decrease the ability of F-adsorption in switching the relative stability of the two surfaces. The present work not only provides new insights into the physical and chemical properties about both pure and F-adsorbed surfaces of TiO2 and conclusively explains related experimental results but also suggests viable ways to prepare TiO2 samples with a high percentage of (001).}, number={10}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Ma, Xiangchao and Dai, Ying and Wei, Wei and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2015}, month={May}, pages={1876–1882} }
 @article{wei_dai_huang_whangbo_jacob_2015, title={Loss of Linear Band Dispersion and Trigonal Structure in Silicene on Ir(111)}, volume={6}, ISSN={["1948-7185"]}, DOI={10.1021/acs.jpclett.5b00106}, abstractNote={The structure of silicene/Ir(111) was examined on the basis of density functional theory. We have found that Ir(111) preserves the 2D character of silicene but significantly distorts its structure from the trigonal one expected for an isolated silicene. The electronic structure of silicene is strongly hybridized with that of Ir(111) so that silicene on Ir(111) loses its linear band dispersion around the Fermi level, giving rise to a metallic band structure; however, silicene/Ir(111) exhibits a hidden linear-dispersive band, which is related to the linear-dispersive conduction band of an isolated silicene.}, number={6}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Wei, Wei and Dai, Ying and Huang, Baibiao and Whangbo, Myung-Hwan and Jacob, Timo}, year={2015}, month={Mar}, pages={1065–1070} }
 @article{zvereva_nalbandyan_evstigneeva_koo_whangbo_ushakov_medvedev_medvedeva_gridina_yalovega_et al._2015, title={Magnetic and electrode properties, structure and phase relations of the layered triangular-lattice tellurate Li4NiTeO6}, volume={225}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2014.12.003}, abstractNote={Abstract We examined the magnetic properties of layered oxide Li4NiTeO6 by magnetic susceptibility, magnetization and ESR measurements and density functional calculations, and characterized phase relations, crystal structure and electrochemical properties of Li4NiTeO6. The magnetization and ESR data indicate the absence of a long-range magnetic order down to 1.8 K, and the magnetic susceptibility data the presence of dominant antiferromagnetic interactions. These observations are well accounted for by density functional calculations, which show that the spin exchanges of the LiNiTeO6 layers in Li4NiTeO6 are strongly spin frustrated. The electrochemical charging of Li4NiTeO6 takes place at constant potential of ca. 4.2 V vs. Li/Li+ indicating two-phase process as confirmed by X-rays. The starting phase is only partially recovered on discharge due to side reactions.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Zvereva, Elena A. and Nalbandyan, Vladimir B. and Evstigneeva, Maria A. and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Ushakov, Arseni V. and Medvedev, Boris S. and Medvedeva, Larisa I. and Gridina, Nelly A. and Yalovega, Galina E. and et al.}, year={2015}, month={May}, pages={89–96} }
 @article{nalbandyan_zvereva_nikulin_shukaev_whangbo_koo_abdel-hafiez_chen_koo_vasiliev_et al._2015, title={New Phase of MnSb2O6 Prepared by Ion Exchange: Structural, Magnetic, and Thermodynamic Properties}, volume={54}, ISSN={["1520-510X"]}, DOI={10.1021/ic502666c}, abstractNote={A new layered trigonal (P3̅1m) form of MnSb2O6, isostructural with MSb2O6 (M = Cd, Ca, Sr, Pb, and Ba) and MAs2O6 (M = Mn, Co, Ni, and Pd), was prepared by ion-exchange reaction between ilmenite-type NaSbO3 and MnSO4–KCl–KBr melt at 470 °C. It is characterized by Rietveld analysis of the X-ray diffraction pattern, electron microprobe analysis, magnetic susceptibility, specific heat, and ESR measurements as well as by density functional theory calculations. MnSb2O6 is very similar to MnAs2O6 in the temperature dependence of their magnetic susceptibility and spin exchange interactions. The magnetic susceptibility and specific heat data show that MnSb2O6 undergoes a long-range antiferromagnetic order with Néel temperature TN = 8.5(5) K. In addition, a weak ferromagnetic component appears below T1 = 41.5(5) K. DFT+U implies that the main spin exchange interactions are antiferromagnetic, thereby forming spin-frustrated triangles. The long-range ordered magnetic structure of MnSb2O6 is predicted to be incommensurate as found for MnAs2O6. On heating, the new phase transforms to the stable P321 form via its intermediate disordered variant.}, number={4}, journal={INORGANIC CHEMISTRY}, author={Nalbandyan, Vladimir B. and Zvereva, Elena A. and Nikulin, Alexey Yu and Shukaev, Igor L. and Whangbo, Myung-Hwan and Koo, Hyun-Joo and Abdel-Hafiez, Mahmoud and Chen, Xiao-Jia and Koo, Changhyun and Vasiliev, Alexander N. and et al.}, year={2015}, month={Feb}, pages={1705–1711} }
 @article{wang_huang_li_wang_qin_zhang_dai_whangbo_2015, title={On Structural Features Necessary for Near-IR-Light Photocatalysts}, volume={21}, ISSN={["1521-3765"]}, DOI={10.1002/chem.201501477}, abstractNote={Abstract In the search for photocatalysts that can directly utilize near‐IR (NIR) light, we investigated three oxides Cu 3 (OH) 4 SO 4 (antlerite), Cu 4 (OH) 6 SO 4 , and Cu 2 (OH) 3 Cl by photodecomposing 2,4‐dichlorophenol over them under NIR irradiation and by comparing their electronic structures with that of the known NIR photocatalyst Cu 2 (OH)PO 4 . Both Cu 3 (OH) 4 SO 4 and Cu 4 (OH) 6 SO 4 are NIR photocatalysts, but Cu 2 (OH) 3 Cl is not. Thus, in addition to the presence of two different CuO m and Cu′O n polyhedra linked with CuOCu′ bridges, the presence of acceptor groups (e.g., SO 4 , PO 4 ) linked to the metal oxygen polyhedra is necessary for NIR photocatalysts.}, number={39}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Wang, Gang and Huang, Baibiao and Li, Zhujie and Wang, Zeyan and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2015}, month={Sep}, pages={13583–13587} }
 @article{kim_yu_kim_koo_whangbo_2015, title={On Why the Two Polymorphs of NaFePO4 Exhibit Widely Different Magnetic Structures: Density Functional Analysis}, volume={54}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.5b00577}, abstractNote={Triphylite-NaFePO4 is a cathode material for Na(+)-ion batteries, whereas its alternative polymorph maricite-NaFePO4 is not. These two different polymorphs exhibit widely different magnetic structures; the ordered magnetic structure of triphylite-NaFePO4 below ∼50 K is described by the propagation vector q1 = (0, 0, 0) with collinear spins, and that of maricite-NaFePO4 below ∼13 K is described by q2 = (1/2, 0, 1/2) with noncollinear spins. We probed the causes for these differences by calculating the spin exchange interactions of the two polymorphs and determining the preferred orientations of their high-spin Fe(2+) (d(6), S = 2) ions on the basis of density functional calculations. Our study shows that maricite-NaFePO4 is not spin-frustrated, which is also the case for triphylite-NaFePO4, that the ordered magnetic structure of triphylite-NaFePO4 is determined mainly by spin exchange, whereas that of maricite-NaFePO4 is determined by both spin exchange and magnetic anisotropy, and that the preferred spin orientations in the two polymorphs can be explained by perturbation theory using spin-orbit coupling as the perturbation.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Kim, Hee Hwan and Yu, Il Han and Kim, Hoon Sik and Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2015}, month={May}, pages={4966–4971} }
 @article{lee_hong_stroppa_whangbo_shim_2015, title={Organic-inorganic hybrid perovskites ABI(3) (A = CH3NH3, NH2CHNH2; B = Sn, Pb) as potential thermoelectric materials: a density functional evaluationt}, volume={5}, ISSN={["2046-2069"]}, DOI={10.1039/c5ra12536g}, abstractNote={Our calculations show that, when doped by electrons, the organic–inorganic perovskite iodides ABI<sub>3</sub>(A = CH<sub>3</sub>NH<sub>3</sub>, NH<sub>2</sub>CHNH<sub>2</sub>; B = Sn, Pb) can be a good thermoelectric material with thermoelectric efficiency comparable to that of hole-doped Bi<sub>2</sub>Te<sub>3</sub>.}, number={96}, journal={RSC ADVANCES}, author={Lee, Changhoon and Hong, Jisook and Stroppa, Alessandro and Whangbo, Myung-Hwan and Shim, Ji Hoon}, year={2015}, pages={78701–78707} }
 @article{galliez_deniard_payen_lambertin_bart_koo_whangbo_jobic_2015, title={Pair Distribution Function and Density Functional Theory Analyses of Hydrogen Trapping by gamma-MnO2}, volume={54}, ISSN={["1520-510X"]}, DOI={10.1021/ic5026334}, abstractNote={In the presence of “Ag2O” as a promoter, γ-MnO2 traps dihydrogen in its (2 × 1) and (1 × 1) tunnels. The course of this reaction was examined by analyzing the X-ray diffraction patterns of the HxMnO2/“Ag2O” system (0 ≤ x < 1) on the basis of pair distribution function and density functional theory (DFT) analyses. Hydrogen trapping occurs preferentially in the (2 × 1) tunnels of γ-MnO2, which is then followed by that in the (1 × 1) tunnels. Our DFT analysis shows that this process is thermodynamically favorable.}, number={4}, journal={INORGANIC CHEMISTRY}, author={Galliez, Kevin and Deniard, Philippe and Payen, Christophe and Lambertin, David and Bart, Florence and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Jobic, Stephane}, year={2015}, month={Feb}, pages={1194–1196} }
 @misc{whangbo_gordon_xiang_koo_lee_2015, title={Prediction of Spin Orientations in Terms of HOMO-LUMO Interactions Using Spin-Orbit Coupling as Perturbation}, volume={48}, ISSN={["1520-4898"]}, DOI={10.1021/acs.accounts.5b00408}, abstractNote={For most chemists and physicists, electron spin is merely a means needed to satisfy the Pauli principle in electronic structure description. However, the absolute orientations of spins in coordinate space can be crucial in understanding the magnetic properties of materials with unpaired electrons. At low temperature, the spins of a magnetic solid may undergo long-range magnetic ordering, which allows one to determine the directions and magnitudes of spin moments by neutron diffraction refinements. The preferred spin orientation of a magnetic ion can be predicted on the basis of density functional theory (DFT) calculations including electron correlation and spin-orbit coupling (SOC). However, most chemists and physicists are unaware of how the observed and/or calculated spin orientations are related to the local electronic structures of the magnetic ions. This is true even for most crystallographers who determine the directions and magnitudes of spin moments because, for them, they are merely the parameters needed for the diffraction refinements. The objective of this article is to provide a conceptual framework of thinking about and predicting the preferred spin orientation of a magnetic ion by examining the relationship between the spin orientation and the local electronic structure of the ion. In general, a magnetic ion M (i.e., an ion possessing unpaired spins) in a solid or a molecule is surrounded with main-group ligand atoms L to form an MLn polyhedron, where n is typically 4-6, and the d states of MLn are split because the antibonding interactions of the metal d orbitals with the p orbitals of the surrounding ligands L depend on the symmetries of the orbitals involved.1 The magnetic ion M of MLn has a certain preferred spin direction because its split d states interact among themselves under SOC.2,3 The preferred spin direction can be readily predicted on the basis of perturbation theory in which the SOC is taken as perturbation and the split d states as unperturbed states by inspecting the magnetic quantum numbers of its d orbitals present in the HOMO and LUMO of the MLn polyhedron. This is quite analogous to how chemists predict whether a chemical reaction is symmetry-allowed or symmetry-forbidden in terms of the HOMO-LUMO interactions by simply inspecting the symmetries of the frontier orbitals.4,5 Experimentally, the determination of the preferred spin orientations of magnetic ions requires a sophisticated level of experiments, for example, neutron diffraction measurements for magnetic solids with an ordered spin state at a very low temperature. Theoretically, it requires an elaborate level of electronic structure calculations, namely, DFT calculations including electron correlation and SOC. We show that the outcomes of such intricate experimental measurements and theoretical calculations can be predicted by a simple perturbation theory analysis.}, number={12}, journal={ACCOUNTS OF CHEMICAL RESEARCH}, author={Whangbo, Myung-Hwan and Gordon, Elijah E. and Xiang, Hongjun and Koo, Hyun-Joo and Lee, Changhoon}, year={2015}, month={Dec}, pages={3080–3087} }
 @article{lee_kim_kim_rhee_whangbo_2015, title={Solution phase post-modification of a trimesic acid network on Au(111) with Zn2+ ions}, volume={51}, ISSN={["1364-548X"]}, DOI={10.1039/c4cc08621j}, abstractNote={Post-modification of a TMA network of crown-like hexamers with Zn<sup>2+</sup> ions transforms it into a metal–organic network of TMA–Zn<sup>2+</sup> coordinated chevron-pairs.}, number={5}, journal={CHEMICAL COMMUNICATIONS}, author={Lee, Jaesung and Kim, Jandee and Kim, Hyeran and Rhee, Choong Kyun and Whangbo, Myung-Hwan}, year={2015}, pages={873–876} }
 @article{canevet_fak_kremer_chun_enderle_gordon_bettis_whangbo_taylor_adroja_2015, title={Spin excitations in the two-dimensional strongly coupled dimer system malachite}, volume={91}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.91.060402}, abstractNote={The mineral malachite, Cu2(OD)2CO3, has a quantum spin-liquid ground state and no long-range magnetic order down to at least T=0.4 K. Inelastic neutron scattering measurements show that the excitation spectrum consists of dispersive gapped singlet-triplet excitations, characteristic of spin-1/2 dimer-forming Heisenberg antiferromagnets. We identify a new two-dimensional dimerized coupling scheme with strong interdimer coupling J'/J1~0.3 that places malachite between strongly coupled alternating chains, square lattice antiferromagnets, and infinite-legged ladders. The geometry of the interaction scheme resembles the staggered dimer lattice, which may allow unconventional quantum criticality.}, number={6}, journal={PHYSICAL REVIEW B}, author={Canevet, E. and Fak, B. and Kremer, R. K. and Chun, J. H. and Enderle, M. and Gordon, E. E. and Bettis, J. L. and Whangbo, M. -H. and Taylor, J. W. and Adroja, D. T.}, year={2015}, month={Feb} }
 @article{wang_huang_li_lou_wang_dai_whangbo_2015, title={Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H-2 production under visible light}, volume={5}, journal={Scientific Reports}, author={Wang, G. and Huang, B. B. and Li, Z. J. and Lou, Z. Z. and Wang, Z. Y. and Dai, Y. and Whangbo, M. H.}, year={2015} }
 @article{read_gordon_smith_yeon_morrison_whangbo_loye_2015, title={Synthesis of the Layered Quaternary Uranium-Containing Oxide Cs2Mn3U6O22 and Characterization of its Magnetic Properties}, volume={54}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.5b00552}, abstractNote={A layered quaternary uranium-containing oxide, Cs2Mn3U6O22, was crystallized from a cesium chloride flux. The crystal structure was determined to consist of α-U3O8 topological layers that are separated by alternating cesium and manganese layers. This ordered arrangement creates a separation between manganese layers of 13 Å, leading to complex low-dimensional magnetic properties. The compound crystallizes in a new structure type in the monoclinic space group, C2/m, with a = 6.8730(10) Å, b = 11.7717(17) Å, c = 13.374(2) Å, and β = 99.673(5)°. The magnetic properties were measured and analyzed by first-principles density functional theory calculations.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Read, Cory M. and Gordon, Elijah E. and Smith, Mark D. and Yeon, Jeongho and Morrison, Gregory and Whangbo, Myung-Hwan and Loye, Hans-Conrad}, year={2015}, month={Jun}, pages={5495–5503} }
 @article{whangbo_gordon_bettis_bussmann-holder_koehler_2015, title={Tolerance Factor and Cation-Anion Orbital Interactions Differentiating the Polar and Antiferrodistortive Structures of Perovskite Oxides ABO(3)}, volume={641}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.201500058}, abstractNote={Abstract We explored under what conditions perovskite oxides ABO 3 adopt a polar or an antiferrodistortive structure from the viewpoint of the tolerance factor τ and the orbital interactions of the empty orbitals of the A and B cations with the filled orbitals of their surrounding O 2– ions. Polar structures require the presence of a substantial size‐mismatch as well as strong cation‐anion orbital interactions at A or B cation sites. A tetragonal polar structure is preferred when the A cation empty orbitals are extended or when the B‐cation empty orbitals are contracted. A trigonal polar structure is favored in opposite cases. An antiferrodistortive structure is found for perovskites with weak size‐mismatch or those with substantial size‐mismatch if both A and B cations do not generate strong cation‐anion orbital interactions. Antiferrodistortive structures result from interactions involving the A cations with the O 4 squares of the face‐sharing A O 8 square‐prisms in a two‐in‐two‐out manner, and are found only when the A/O cation‐anion interactions are substantial.}, number={6}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Whangbo, Myung-Hwan and Gordon, Elijah E. and Bettis, Jerry L., Jr. and Bussmann-Holder, Annette and Koehler, Juergen}, year={2015}, month={May}, pages={1043–1052} }
 @article{bussmann-holder_koehler_whangbo_2015, title={Unexpected Precursor Effects to the Structural Phase Transition in EuTiO3}, volume={641}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.201400596}, abstractNote={Abstract The dynamical properties of EuTiO 3 are investigated to gain insight into its precursor effects analogous to those observed in many other perovskite oxides. In spite of the fact that a competition between the long wave length transverse optic mode and the zone boundary acoustic mode is absent, which makes the mode‐mode coupling inessential, acoustic instabilities on limited spatial regions appear well above T S . This confirms the notion that dynamic forerunners are inherent and precede any phase transition in cubic perovskite oxides.}, number={2}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Bussmann-Holder, Annette and Koehler, Juergen and Whangbo, Mike-H.}, year={2015}, month={Feb}, pages={180–183} }
 @article{lou_huang_wang_ma_zhang_zhang_qin_dai_whangbo_2014, title={Ag6Si2O7: a Silicate Photocatalyst for the Visible Region}, volume={26}, ISSN={["1520-5002"]}, DOI={10.1021/cm500657n}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTAg6Si2O7: a Silicate Photocatalyst for the Visible RegionZaizhu Lou†, Baibiao Huang*†, Zeyan Wang†, Xiangchao Ma‡, Rui Zhang†‡, Xiaoyang Zhang†, Xiaoyan Qin†, Ying Dai‡, and Myung-Hwan Whangbo§View Author Information‡ †State Key Laboratory of Crystal Materials and ‡School of Physics, Shandong University, Jinan 250100, P. R. China§ Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States*E-mail: [email protected]Cite this: Chem. Mater. 2014, 26, 13, 3873–3875Publication Date (Web):June 12, 2014Publication History Received24 February 2014Revised10 June 2014Published online16 June 2014Published inissue 8 July 2014https://doi.org/10.1021/cm500657nCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2723Altmetric-Citations113LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Catalytic activity,Degradation,Electrical conductivity,Photocatalysis,Photocatalysts Get e-Alerts}, number={13}, journal={CHEMISTRY OF MATERIALS}, author={Lou, Zaizhu and Huang, Baibiao and Wang, Zeyan and Ma, Xiangchao and Zhang, Rui and Zhang, Xiaoyang and Qin, Xiaoyan and Dai, Ying and Whangbo, Myung-Hwan}, year={2014}, month={Jul}, pages={3873–3875} }
 @article{lee_kang_hong_shim_whangbo_2014, title={Analysis of the Difference between the Pyroxenes LiFeSi2O6 and LiFeGe2O6 in Their Spin Order, Spin Orientation, and Ferrotoroidal Order}, volume={26}, ISSN={["1520-5002"]}, DOI={10.1021/cm5001413}, abstractNote={The pyroxenes LiFeSi2O6 and LiFeGe2O6 are isostructural and isoelectronic, but they differ in their spin order, spin orientation and ferrotoroidal order. The reasons for these differences were probed by density functional theory electronic structure calculations and magnetic dipole–dipole (MDD) interaction energy calculations. The ferromagnetic Fe-zigzag chains of LiFeSi2O6 arise from the antiferromagnetic interchain spin exchanges and the antiferromagnetic Fe-zigzag chains of LiFeGe2O6 from the antiferromagnetic intrachain spin exchange. The preferred spin orientations of LiFeGe2O6 and LiFeSi2O6 are not caused by spin–orbit coupling but by MDD interactions. LiFeSi2O6 undergoes a ferrotoroidal order because it has spin exchange rings made up of an even number of antiferromagnetic spin exchanges paths with comparable strengths. A ferrotoroidal order is not expected for LiFeGe2O6 because it has no such spin exchange rings.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Kang, Jinhee and Hong, Jisook and Shim, Ji Hoon and Whangbo, Myung-Hwan}, year={2014}, month={Feb}, pages={1745–1750} }
 @article{caslin_kremer_razavi_schulz_munoz_pertlik_liu_whangbo_law_2014, title={Characterization of the spin-1/2 linear-chain ferromagnet CuAs2O4}, volume={89}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.89.014412}, abstractNote={The magnetic and lattice properties of the $S$=1/2 quantum-spin-chain ferromagnet, CuAs$_2$O$_4$, mineral name trippkeite, were investigated. The crystal structure of CuAs$_2$O$_4$ is characterized by the presence of corrugated CuO$_2$ ribbon chains. Measurements of the magnetic susceptibility, heat capacity, electron paramagnetic resonance and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic transition occurs at $\sim$7.4 K. $\textit{Ab initio}$ DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next- nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of $J_{\rm nn}$/$J_{\rm nnn}$ is near -4, placing CuAs$_2$O$_4$ in close proximity to a quantum critical point in the $J_{\rm nn}$ - $J_{\rm nnn}$ phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu$^{2+}$ spins to lie in an easy plane perpendicular to the $c$-axis. An analysis of the field and temperature dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasi-hydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy.}, number={1}, journal={PHYSICAL REVIEW B}, author={Caslin, K. and Kremer, R. K. and Razavi, F. S. and Schulz, A. and Munoz, A. and Pertlik, F. and Liu, J. and Whangbo, M. -H. and Law, J. M.}, year={2014}, month={Jan} }
 @article{hu_johnsson_law_bettis_whangbo_kremer_2014, title={Crystal Structure and Magnetic Properties of FeSeO3F-Alternating Antiferromagnetic S=5/2 chains}, volume={53}, ISSN={["1520-510X"]}, DOI={10.1021/ic5003995}, abstractNote={The new oxofluoride FeSeO3F, which is isostructural with FeTeO3F and GaTeO3F, was prepared by hydrothermal synthesis, and its structure was determined by X-ray diffraction. The magnetic properties of FeSeO3F were characterized by magnetic susceptibility and specific heat measurements, by evaluating its spin exchanges on the basis of density functional theory (DFT) calculations, and by performing a quantum Monte Carlo simulation of the magnetic susceptibility. FeSeO3F crystallizes in the monoclinic space group P21/n and has one unique Se4+ ion and one unique Fe3+ ion. The building blocks of FeSeO3F are [SeO3] trigonal pyramids and cis-[FeO4F2] distorted octahedra. The cis-[FeO4F2] octahedra are condensed by sharing the O–O and F–F edges alternatingly to form [FeO3F]∞ chains, which are interconnected via the [SeO3] pyramids by corner-sharing. The magnetic susceptibility of FeSeO3F is characterized by a broad maximum at 75(2) K and a long-range antiferromagnetic order below ∼45 K. The latter is observed by magnetic susceptibility and specific heat measurements. DFT calculations show that the Fe–F–Fe spin exchange is stronger than the Fe–O–Fe exchange, so each [FeO3F]∞ chain is a Heisenberg antiferromagnetic chain with alternating antiferromagnetic spin exchanges. The temperature dependence of the magnetic susceptibility is well-reproduced by a quantum-Monte Carlo simulation.}, number={8}, journal={INORGANIC CHEMISTRY}, author={Hu, Shichao and Johnsson, Mats and Law, Joseph M. and Bettis, Jerry L., Jr. and Whangbo, Myung-Hwan and Kremer, Reinhard K.}, year={2014}, month={Apr}, pages={4250–4256} }
 @article{koo_whangbo_2014, title={Density functional investigation of why Ba2BiFeS5 and Ba2SbFeS5 differ in their magnetic properties}, volume={360}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2014.02.024}, abstractNote={We examined the cause for the difference in the magnetic properties of the isostructural/isoelectronic compounds Ba2SbFeS5 and Ba2BiFeS5 by evaluating their spin exchange parameters on the basis of density functional theory calculations. The difference is traced to the exchange triangle made up of three strongly antiferromagnetic spin exchange paths, which exhibits stronger spin frustration for Ba2SbFeS5 than for Ba2BiFeS5.}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2014}, month={Jun}, pages={152–156} }
 @article{ma_dai_yu_lou_huang_whangbo_2014, title={Electron Hole Pair Generation of the Visible-Light Plasmonic Photocatalyst Ag@AgCl: Enhanced Optical Transitions Involving Midgap Defect States of AgCl}, volume={118}, ISSN={["1932-7455"]}, DOI={10.1021/jp5023604}, abstractNote={We explored how the visible-light energy absorbed by noble-metal nanoparticles (NPs) is converted to electrons and holes in the semiconductor in a visible-light plasmonic photocatalyst by studying the representative system Ag@AgCl on the basis of density functional calculations and classical electrodynamics calculations. These calculations suggest that the energy transfer from the Ag NPs to the semiconductor AgCl requires the presence of midgap defect states in the semiconductor and that the surface plasmon resonance (SPR) of the Ag NPs strongly enhances the optical transitions of the semiconductor involving the defect states. We verified this suggestion experimentally by preparing Ag@AgCl samples possessing different degrees of bulk and surface defects and subsequently by carrying out photodegradation experiments using these samples.}, number={23}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Ma, Xiangchao and Dai, Ying and Yu, Lin and Lou, Zaizhu and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2014}, month={Jun}, pages={12133–12140} }
 @article{lee_lee_lee_whangbo_2014, title={Evaluating the Curie-Weiss Temperature of a Magnetic System Composed of Nonequivalent Magnetic Ions in Terms of Spin Exchange Constants}, volume={35}, ISSN={["1229-5949"]}, DOI={10.5012/bkcs.2014.35.5.1277}, abstractNote={E-mail: mike_whangbo@ncsu.eduReceived January 18, 2014, Accepted February 5, 2014Key Words : Nonequivalent magnetic ions, Curie-Weiss temperature, Mean field theory, Spin exchange pa-rameters, Density functional theory Magnetic properties of a system containing magnetic ionsare related to its electronic structure,}, number={5}, journal={BULLETIN OF THE KOREAN CHEMICAL SOCIETY}, author={Lee, Kee Hag and Lee, Ji Young and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2014}, month={May}, pages={1277–1278} }
 @article{mccabe_stock_bettis_whangbo_evans_2014, title={Magnetism of the Fe2+ and Ce3+ sublattices in Ce2O2FeSe2: A combined neutron powder diffraction, inelastic neutron scattering, and density functional study}, volume={90}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.90.235115}, abstractNote={The discovery of superconductivity in the 122 iron selenide materials above 30 K necessitates an understanding of the underlying magnetic interactions. We present a combined experimental and theoretical investigation of magnetic and semiconducting ${\mathrm{Ce}}_{2}{\mathrm{O}}_{2}{\mathrm{FeSe}}_{2}$ composed of chains of edge-linked iron selenide tetrahedra. The combined neutron diffraction and inelastic scattering study and density functional calculations confirm the ferromagnetic nature of nearest-neighbor Fe-Se-Fe interactions in the ZrCuSiAs-related iron oxyselenide ${\mathrm{Ce}}_{2}{\mathrm{O}}_{2}{\mathrm{FeSe}}_{2}$. Inelastic measurements provide an estimate of the strength of nearest-neighbor Fe-Fe and Fe-Ce interactions. These are consistent with density functional theory calculations, which reveal that correlations in the Fe-Se sheets of ${\mathrm{Ce}}_{2}{\mathrm{O}}_{2}{\mathrm{FeSe}}_{2}$ are weak. The Fe on-site repulsion ${U}_{Fe}$ is comparable to that reported for oxyarsenides and ${\mathrm{K}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{2\ensuremath{-}y}{\mathrm{Se}}_{2}$, which are parents to iron-based superconductors.}, number={23}, journal={PHYSICAL REVIEW B}, author={McCabe, E. E. and Stock, C. and Bettis, J. L., Jr. and Whangbo, M. -H. and Evans, J. S. O.}, year={2014}, month={Dec} }
 @article{liu_koo_xiang_kremer_whangbo_2014, title={Most spin-1/2 transition-metal ions do have single ion anisotropy}, volume={141}, number={12}, journal={Journal of Chemical Physics}, author={Liu, J. and Koo, H. J. and Xiang, H. J. and Kremer, R. K. and Whangbo, M. H.}, year={2014} }
 @article{koo_whangbo_2014, title={Spin Exchange and Magnetic Dipole Dipole Interactions Leading to the Magnetic Superstructures of MAs2O6 (M = Mn, Co, Ni)}, volume={53}, ISSN={["1520-510X"]}, DOI={10.1021/ic500156e}, abstractNote={The three isostructural magnetic oxides MAs2O6 (M = Mn, Co, Ni) containing high-spin M2+ ions undergo a long-range antiferromagnetic ordering below 30 K, but their ordered magnetic structures are not identical. While CoAs2O6 and NiAs2O6 adopt the commensurate superstructure of q1 = (0, 0, 1/2), MnAs2O6 has the incommensurate superstructure of q2 = (0.055, 0.389, 0.136). The cause for this difference was examined by calculating their spin exchange and magnetic dipole–dipole interaction energies. In CoAs2O6 and NiAs2O6, the strongest M–O···O–M spin exchange, J1, dominates over other exchanges, hence leading to the q1 superstructure. For MnAs2O6, the spin exchanges are not a deciding factor leading to its magnetic superstructure, being all weak and comparable in strengths, but the magnetic dipole–dipole interactions are.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2014}, month={Apr}, pages={3812–3817} }
 @article{ma_dai_wei_huang_whangbo_2014, title={Strain-induced quantum spin Hall effect in methyl-substituted germanane GeCH3}, volume={4}, journal={Scientific Reports}, author={Ma, Y. D. and Dai, Y. and Wei, W. and Huang, B. B. and Whangbo, M. H.}, year={2014} }
 @article{law_koo_whangbo_bruecher_pomjakushin_kremer_2014, title={Strongly correlated one-dimensional magnetic behavior of NiTa2O6}, volume={89}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.89.014423}, abstractNote={The magnetic properties of NiTa${}_{2}$O${}_{6}$ were investigated by magnetic susceptibility, specific heat, electron paramagnetic resonance, neutron powder diffraction, and pulse field magnetization measurements. Accompanying ab initio DFT calculations of the spin-exchange constants complemented and supported our experimental findings that NiTa${}_{2}$O${}_{6}$ must be described as a quasi-1D Heisenberg $S=1$ spin chain system with a nearest-neighbor only antiferromagnetic spin-exchange interaction of 18.92(2) K. Interchain coupling is by about two orders of magnitude smaller. Electron paramagnetic resonance measurements on Mg${}_{1\ensuremath{-}x}$Ni${}_{x}$Ta${}_{2}$O${}_{6}$ ($x\ensuremath{\approx}1%$) polycrystalline samples enabled us to estimate the single-ion zero-field splitting of the $S=1$ states which amounts to less than 4% of the nearest-neighbor spin-exchange interaction. At 0 T NiTa${}_{2}$O${}_{6}$ undergoes long-range antiferromagnetic ordering at 10.3(1) K evidenced by a $\ensuremath{\lambda}$-type anomaly in the specific heat capacity. On application of a magnetic field the specific heat anomaly is smeared out. We confirmed the magnetic structure by neutron powder diffraction measurements and at 2.00(1) K refined a magnetic moment of 1.93(5) ${\ensuremath{\mu}}_{\mathrm{B}}$ per Ni${}^{2+}$ ion. Additionally, we followed the magnetic order parameter as a function of temperature. Last, we found saturation of the magnetic moment at 55.5(5) T with a $g$ factor of 2.14(1), with an additional high field phase above 12.8(1) T. The onset of the new high field phase is not greatly affected by temperature, but rather smears out as one approaches the long-range ordering temperature.}, number={1}, journal={PHYSICAL REVIEW B}, author={Law, J. M. and Koo, H. -J. and Whangbo, M. -H. and Bruecher, E. and Pomjakushin, V. and Kremer, R. K.}, year={2014}, month={Jan} }
 @article{stroppa_di sante_barone_bokdam_kresse_franchini_whangbo_picozzi_2014, title={Tunable ferroelectric polarization and its interplay with spin-orbit coupling in tin iodide perovskites}, volume={5}, journal={Nature Communications}, author={Stroppa, A. and Di Sante, D. and Barone, P. and Bokdam, M. and Kresse, G. and Franchini, C. and Whangbo, M. H. and Picozzi, S.}, year={2014} }
 @article{david_kabbour_pautrat_touati_whangbo_mentre_2014, title={Two-Orbital Three-Electron Stabilizing Interaction for Direct Co2+ - As3+ Bonds involving Square-Planar CoO4 in BaCoAs2O5}, volume={53}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201311183}, abstractNote={Abstract The quest for new oxides with cations containing active lone‐pair electrons ( E ) covers a broad field of targeted specificities owing to asymmetric electronic distribution and their particular band structure. Herein, we show that the novel compound BaCoAs 2 O 5 , with lone‐pair As 3+ ions, is built from rare square‐planar Co 2+ O 4 involved in direct bonding between As 3+ E and Co 2+ d z 2 orbitals (CoAs=2.51 Å). By means of DFT and Hückel calculations, we show that this σ‐type overlapping is stabilized by a two‐orbital three‐electron interaction allowed by the high‐spin character of the Co 2+ ions. The negligible experimental spin‐orbit coupling is expected from the resulting molecular orbital scheme in O 3 As E –CoO 4 clusters.}, number={12}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={David, Renald and Kabbour, Houria and Pautrat, Alain and Touati, Nadia and Whangbo, Myung-Hwan and Mentre, Olivier}, year={2014}, month={Mar}, pages={3111–3114} }
 @article{bao_ma_chen_xu_enriquez_chen_zhang_bettis_whangbo_dong_et al._2014, title={Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo(2)O(5.5+delta) thin films}, volume={4}, journal={Scientific Reports}, author={Bao, S. Y. and Ma, C. R. and Chen, G. and Xu, X. and Enriquez, E. and Chen, C. L. and Zhang, Y. M. and Bettis, J. L. and Whangbo, M. H. and Dong, C. and et al.}, year={2014} }
 @article{wang_bao_liu_collins_ma_liu_chen_dong_whangbo_guo_et al._2014, title={Ultrafast chemical dynamic behavior in highly epitaxial LaBaCo2O5+delta thin films}, volume={2}, ISSN={["2050-7534"]}, DOI={10.1039/c4tc00492b}, abstractNote={The redox reactions of highly epitaxial LaBaCo<sub>2</sub>O<sub>5+δ</sub> (LBCO) thin films exposed to the switching flow of reducing (H<sub>2</sub>) and oxidizing (O<sub>2</sub>) gases were examined at various temperatures between 260 and 700 °C. Their electrical resistance was measured using a precise ac bridge measurement system.}, number={28}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Wang, H. B. and Bao, S. Y. and Liu, J. and Collins, G. and Ma, C. R. and Liu, M. and Chen, C. L. and Dong, C. and Whangbo, M. -H. and Guo, H. M. and et al.}, year={2014}, pages={5660–5666} }
 @article{kim_rhee_koo_kasapbasi_whangbo_2013, title={A Contoured Network of Anionic Trimesic Acids on Au(111) and Its Host-Guest Chemistry}, volume={117}, ISSN={["1932-7455"]}, DOI={10.1021/jp403203s}, abstractNote={This work describes a trimesic acid (TMA) network formed at the open-circuit potential (OCP, ∼0.13 V) on Au(111), which we investigate with electrochemical scanning tunneling microscopy (STM). The unit cell of the TMA network at the OCP was (5√3 × 5√3)R30°–4TMA, while that of a well-known honeycomb network of flat-lying TMAs at −0.1 V was (6 × 6)R30°–2TMA. The most significant difference between the two networks is the fraction of hydrogen bonds appearing as bright spots in the STM images: it is 1/3 in the former but 1 in the latter. Additional differences were the shapes and lengths of the STM spots and the packing density of TMAs. A contoured network composed of crownlike anionic TMA hexamers was proposed to explain all the differences. The TMAs in the crownlike hexamer were rotated along the molecular axis and were tilted up from the surface by ∼30° to have hydrogen bonds with reasonable O–H···O distance, and the hexamers were interconnected to a contoured network. The existence of the anionic TMA hexamer was evidenced by selective host–guest interaction of Cu2+ ions and 1-mercaptohexane with the contoured network. At a higher potential than the OCP, simple arrays of anionic TMA dimers with much higher packing densities were observed, depending on the availability of TMAs from solution. The potential dependence of the structure of the TMA adlayer is discussed in terms of a transition from molecular adsorption to anionic adsorption.}, number={44}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kim, Jandee and Rhee, Choong K. and Koo, Hyun-J. and Kasapbasi, Emine E. and Whangbo, Myung-H.}, year={2013}, month={Nov}, pages={22636–22643} }
 @article{jin_kim_jo_bettis_koo_whangbo_hwang_2013, title={A Crucial Role of Bond Covalency Competition in Determining the Bandgap and Photocatalytic Performance of Silver Oxosalts}, volume={117}, ISSN={["1932-7455"]}, DOI={10.1021/jp4101784}, abstractNote={The optical bandgaps, the surface charges, and the photocatalytic activities of the silver oxosalts Ag3AsO4, Ag2CO3, Ag3PO4, Ag2SO4, and Ag2SeO4 are systematically investigated with several experimental techniques and first principles density functional theory calculations. The trends in the optical bandgaps and the surface charges of these silver oxosalts, Agx(XOy)z, are analyzed by considering how the X–O bond covalency affects the charge on the terminal oxygen atoms and the Ag–O bond covalency. The optical bandgaps of Agx(XOy)z are well-described by the bond-covalency competition in the Ag–O–X linkages because an increase in the overlap between the O 2s/2p and X ns/np orbitals decreases the overlap between the Ag 4d and O 2s/2p orbitals. The optical bandgap increases linearly with increasing the Z/r ratio of the atom X, a simple measure of the X–O bond covalency. In the photodegradation of charged molecules, the surface charge of Agx(XOy)z plays a prominent role and decreases with increasing the Z/r ratio. As expected from the present theoretical predictions, newly investigated Ag2SeO4 exhibits a promising photocatalytic activity under visible light. The Z/r ratio of the central atom X provides an effective measure for predicting the photocatalyst performance and the optical bandgap of silver oxosalts Agx(XOy)z.}, number={50}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Jin, Xiaoyan and Kim, In Young and Jo, Yun Kyung and Bettis, Jerry L., Jr. and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Hwang, Seong-Ju}, year={2013}, month={Dec}, pages={26509–26516} }
 @article{david_pautrat_filimonov_kabbour_vezin_whangbo_mentre_2013, title={Across the Structural Re-Entrant Transition in BaFe2(PO4)(2): Influence of the Two-Dimensional Ferromagnetism}, volume={135}, ISSN={["0002-7863"]}, DOI={10.1021/ja404697b}, abstractNote={BaFe2(PO4)2 was recently prepared by hydrothermal synthesis and identified as the first two-dimensional (2D) Ising ferromagnetic oxide, in which honeycomb layers made up of edge-sharing FeO6 octahedra containing high-spin Fe2+ ions (S = 2) are isolated by PO4 groups and Ba2+ cations. BaFe2(PO4)2 has a trigonal R-3 structure at room temperature but adopts a triclinic P-1 structure below 140 K due to the Jahn–Teller (JT) instability arising from the (t2g)4(eg)2 configuration. The triclinic crystal structure was refined to find significantly distorted Fe2+O6 octahedra in the honeycomb layers while the distortion amplitude QJT was estimated to 0.019 Å. The JT stabilization energy is estimated to be ∼7 meV per formula unit by DFT calculations. Below ∼70 K, very close to the ferromagnetic transition temperature Tc = 65.5 K, the structure of BaFe2(PO4)2 returns to a trigonal R-3 structure in the presence of significant ferromagnetic domains. This rare re-entrant structural transition is accompanied by a discontinuous change in the quadrupolar splitting of Fe2+, as determined by Mössbauer spectroscopy. EPR measurements show the presence of magnetic domains well above Tc , as expected for a ferromagnetic 2D Ising system, and support that the magnetism of BaFe2(PO4)2 is uniaxial (g⊥ = 0).}, number={35}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={David, Renald and Pautrat, Alain and Filimonov, Dmitry and Kabbour, Houria and Vezin, Herve and Whangbo, Myung-Hwan and Mentre, Olivier}, year={2013}, month={Sep}, pages={13023–13029} }
 @article{lapidus_manson_park_clement_ghannadzadeh_goddard_lancaster_moeller_blundell_telling_et al._2013, title={Antiferromagnetic ordering through a hydrogen-bonded network in the molecular solid CuF2(H2O)(2)(3-chloropyridine)}, volume={49}, ISSN={["1359-7345"]}, DOI={10.1039/c2cc37444g}, abstractNote={CuF(2)(H(2)O)(2)(3-chloropyridine) possesses a five-coordinate Cu(2+) center with a slightly distorted trigonal bypyramidal coordination geometry. Strong intermolecular F···H-O hydrogen bonds enable the formation of 2D layers and provide the primary magnetic exchange path that leads to the stabilization of long-range antiferromagnetic (AFM) order below T(N) = 2.1 K.}, number={5}, journal={CHEMICAL COMMUNICATIONS}, author={Lapidus, Saul H. and Manson, Jamie L. and Park, Hyunsoo and Clement, Alexander J. and Ghannadzadeh, Saman and Goddard, Paul and Lancaster, Tom and Moeller, Johannes S. and Blundell, Stephen J. and Telling, Mark T. F. and et al.}, year={2013}, pages={499–501} }
 @article{wang_huang_ma_wang_qin_zhang_dai_whangbo_2013, title={Cu2(OH)PO4, a Near-Infrared-Activated Photocatalyst}, volume={52}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201301306}, abstractNote={Crystal power! Libethenite, Cu2(OH)PO4 (see 4–5 μm×1.5 μm image), absorbs strongly in the near-infrared (NIR) region and is an effective photocatalyst for the decomposition of 2,4-dichlorophenol in aqueous solution under NIR irradiation. This NIR activation of the photocatalyst is due to a facile transfer of photogenerated electrons from the trigonal bipyramidal CuII sites to the adjacent octahedral CuII sites.}, number={18}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Wang, Gang and Huang, Baibiao and Ma, Xiangchao and Wang, Zeyan and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2013}, pages={4810–4813} }
 @article{wang_jain_choi_tol_cheetham_kroto_koo_zhou_hwang_choi_et al._2013, title={Dimethylammonium copper formate [(CH3)(2)NH2]Cu(HCOO)(3): A metal-organic framework with quasi-one-dimensional antiferromagnetism and magnetostriction}, volume={87}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.87.224406}, abstractNote={Metal-organic frameworks (MOFs) can exhibit many interesting properties such as multiferroic behavior, dipolar glass, gas storage, and protonic conductivity. Here we report that dimethylammonium copper formate (DMACuF) [(CH${}_{3}$)${}_{2}$NH${}_{2}$]Cu(HCOO)${}_{3}$, a cation templated nonporous MOF with perovskite topology, exhibits strong one-dimensional (1D) antiferromagnetism with a N\'eel temperature, ${T}_{N}$, of 5.2 K. These conclusions are derived from detailed magnetic susceptibility, heat capacity, dielectric constant, and high-frequency electron paramagnetic resonance measurements as well as density functional theory (DFT) calculations. The magnetic susceptibility exhibits a broad maximum at \ensuremath{\sim}50 K, suggesting low-dimensional magnetism; heat capacity measurements show a N\'eel temperature of 5.2 K. The magnetization versus field data at 1.8 K shows a spin-flop transition at ${H}_{sf}$ \ensuremath{\sim} 1.7 T. The ratio ${T}_{N}$/$J=6.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$, where $J$ is the near-neighbor exchange constant (77.4 K), and the small value (2 K) of the interchain coupling suggests that DMACuF is close to an ideal 1D magnet. In this three-dimensional crystal lattice, the 1D magnetic behavior is made possible by the Jahn-Teller distortion of the 3${d}^{9}$ Cu${}^{2+}$ ions. Temperature dependence of the electron paramagnetic resonance field and the linewidth exhibits critical broadening for temperatures below 50 K, following a behavior quite characteristic of 1D spin systems. DFT calculations show that [(CH${}_{3}$)${}_{2}$NH${}_{2}$]Cu(HCOO)${}_{3}$ has a magnetic structure in which 1D antiferromagnetic chains parallel to the $c$ direction are weakly coupled ferromagnetically, supporting the thermomagnetic and EPR results. Dielectric measurements under applied magnetic fields of 0\ensuremath{-}7 T reveal a kink at the ${T}_{N}$, a clear indication of magnetostriction behavior.}, number={22}, journal={PHYSICAL REVIEW B}, author={Wang, Zhenxing and Jain, Prashant and Choi, Kwang-Yong and Tol, Johan and Cheetham, Anthony K. and Kroto, Harold W. and Koo, Hyun-Joo and Zhou, Haidong and Hwang, Jungmin and Choi, Eun Sang and et al.}, year={2013}, month={Jun} }
 @article{wang_huang_ma_wang_qin_zhang_dai_whangbo_2013, title={Efficient Separation of Photogenerated Electron-Hole Pairs by the Combination of a Heterolayered Structure and Internal Polar Field in Pyroelectric BiOIO3 Nanoplates}, volume={19}, ISSN={["1521-3765"]}, DOI={10.1002/chem.201302884}, abstractNote={Electrify your chemistry! Pyroelectric heterolayered BiOIO3 nanoplates efficiently separate photogenerated electron-hole pairs due to the combined effect of their heterolayered structure and internal polar field (see scheme). Pyroelectric BiOIO3 nanoplates, synthesized by a simple hydrothermal method, were found to possess a superior photocatalytic activity under UV irradiation. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={44}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Wang, Wenjun and Huang, Baibiao and Ma, Xiangchao and Wang, Zeyan and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2013}, month={Oct}, pages={14777–14780} }
 @article{lee_hong_whangbo_shim_2013, title={Enhancing the Thermoelectric Properties of Layered Transition-Metal Dichalcogenides 2H-MQ(2) (M = Mo, W; Q = S, Se, Te) by Layer Mixing: Density Functional Investigation}, volume={25}, ISSN={["1520-5002"]}, DOI={10.1021/cm402281n}, abstractNote={We explored how to improve the thermoelectric properties of the layered transition-metal dichalcogenides 2H-MQ2 (M = Mo, W; Q = S, Se, Te) by comparing the thermoelectric properties of hypothetical mixed-layer systems 2H-MQ2/2H-MQ′2, in which two different layers 2H-MQ2 and 2H-MQ′2 (Q, Q′ = S, Se, Te) alternate, with those of their pure components on the basis of density functional calculations. Our study predicts that the mixed-layer compounds MS2/MTe2 (M = Mo, W) strongly enhance the thermoelectric properties as a consequence of reducing the band gap and the interlayer van der Waals interactions. The layer-mixing is predicted to be a promising way of improving the thermoelectric properties of 2H-MQ2.}, number={18}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Hong, Jisook and Whangbo, Myung-Hwan and Shim, Ji Hoon}, year={2013}, month={Sep}, pages={3745–3752} }
 @article{jeong_kim_cha_son_park_kim_cho_whangbo_yoo_kim_2013, title={Hydrogen Sensing under Ambient Conditions Using SnO2 Nanowires: Synergetic Effect of Pd/Sn Codeposition}, volume={13}, ISSN={["1530-6992"]}, DOI={10.1021/nl402998g}, abstractNote={Semiconducting SnO2 nanowires deposited with Pd and Sn nanoparticles on their surface are shown to be a highly sensitive hydrogen sensor with fast response time at room temperature. Compared with the SnO2 nanowire deposited with Pd or Sn nanoparticles alone, the Pd/Sn-deposited SnO2 nanowire exhibits a significant improvement in the sensitivity and reversibility of sensing hydrogen gas in the air at room temperature. Our investigation indicates that two factors are responsible for the synergistic effect of Pd/Sn codeposition on SnO2 nanowires. One is that in the presence of Pd the oxidation of Sn nanoparticles on the surface of the SnO2 nanowire is incomplete leading only to suboxides SnOx (1 ≤ x < 2), and the other is that the surface of the Pd/Sn-deposited SnO2 nanowire is almost perfectly hydrophobic.}, number={12}, journal={NANO LETTERS}, author={Jeong, Seung Ho and Kim, Sol and Cha, Junho and Son, Min Soo and Park, Sang Han and Kim, Ha-Yeong and Cho, Man Ho and Whangbo, Myung-Hwan and Yoo, Kyung-Hwa and Kim, Sung-Jin}, year={2013}, month={Dec}, pages={5938–5943} }
 @article{lou_huang_wang_qin_zhang_liu_zhang_dai_whangbo_2013, title={Interface kinetic diffusion reaction leading to fast and continuous generation of AgCl nanocubes in NaCl solution}, volume={42}, number={42}, journal={Dalton Transactions (Cambridge, England : 2003)}, author={Lou, Z. Z. and Huang, B. B. and Wang, Z. Y. and Qin, X. Y. and Zhang, X. Y. and Liu, Y. Y. and Zhang, R. and Dai, Y. and Whangbo, M. H.}, year={2013}, pages={15219–15225} }
 @article{nenert_koo_colin_bauer_bellitto_ritter_righini_whangbo_2013, title={Magnetic Order Through Super-Superexchanges in the Polar Magnetoelectric Organic-Inorganic Hybrid Cr[(D3N-(CH2)(2)-PO3)(Cl)(D2O)]}, volume={52}, ISSN={["1520-510X"]}, DOI={10.1021/ic301874v}, abstractNote={The crystal and magnetic structures of the organic–inorganic hybrid compound Cr(II) ammoniumethylphosphonate chloride monohydrate, Cr[D3N-(CH2)2-PO3)(Cl)(D2O)] (1), have been studied by temperature-dependent neutron powder diffraction and superconducting quantum interference device (SQUID) magnetometry. The compound represents a rare example of a magnetoelectric polar organic–inorganic hybrid solid, containing high spin Cr2+ ions (S = 2) and is a canted antiferromagnet (weak ferromagnet) below TN = 5.5 K. The neutron powder diffraction pattern recorded at T = 10 K, shows that the partially deuterated compound crystallizes in the same non centrosymmetric monoclinic space group P21 (No. 4) with the following unit-cell parameters: a = 5.24041(4) Å, b =13.93113(8) Å, c = 5.26081(4) Å, and β = 105.4347(5)°. Powder neutron diffraction of a partially deuterated sample has enabled us, for the first time, to locate the water molecule. At low temperature, the compound presents a canted antiferromagnetic state characterized by k = 0 resulting in the magnetic symmetry P21′. This symmetry is in agreement with the previously reported large magnetodielectric effect. The crystal structure of (1) can be described as being built up of triangular lattice planes made up of [Cr(II)O4Cl] square pyramids which are separated by ammonium ethyl groups along the b axis. The transition from paramagnetic to weakly ferromagnetic state results from super-superexchanges only. Surprisingly, while the overall magnetic behavior is antiferromagnetic, the Cr(II)O4Cl planes are ferromagnetic, and the strongest antiferromagnetic coupling is via the ammonium ethyl groups. Our density functional calculations confirm these aspects of the spin exchange interactions of (1) and that the spin exchange interactions between Cr(II) ions are considerably weak compared with the single-ion anisotropy of CrII.}, number={2}, journal={INORGANIC CHEMISTRY}, author={Nenert, Gwilherm and Koo, Hyun-Joo and Colin, Claire V. and Bauer, Elvira M. and Bellitto, Carlo and Ritter, Clemens and Righini, Guido and Whangbo, Myung-Hwan}, year={2013}, month={Jan}, pages={753–760} }
 @article{nenert_bettis_kremer_ben yahia_ritter_gaudin_isnard_whangbo_2013, title={Magnetic Properties of the RbMnPO4 Zeolite-ABW-Type Material: A Frustrated Zigzag Spin Chain}, volume={52}, ISSN={["1520-510X"]}, DOI={10.1021/ic401408f}, abstractNote={The crystal structure and magnetic properties of the RbMnPO4 zeolite-ABW type material have been studied by temperature-dependent neutron powder diffraction, low temperature magnetometry and heat capacity measurements. RbMnPO4 represents a rare example of a weak ferromagnetic polar material, containing Mn2+ ions with TN = 4.7 K. The neutron powder diffraction pattern recorded at T = 10 K shows that the compound crystallizes in the chiral and polar monoclinic space group P21 (No. 4) with the unit-cell parameters: a = 8.94635(9) {\AA}, b = 5.43415(5) {\AA}, c = 9.10250(8) {\AA} and beta = 90.4209(6){\deg}. A close inspection of the crystal structure of RbMnPO4 shows that this material presents two different types of zigzag chains running along the b axis. This is a unique feature among the zeolite-ABW type materials exhibiting the P21 symmetry. At low temperature, RbMnPO4 exhibits a canted antiferromagnetic structure characterized by the propagation vector k1 = 0 resulting in the magnetic symmetry P21. The magnetic moments lie mostly along the b axis with the ferromagnetic component being in the ac plane. Due to the geometrical frustration present in this system, an intermediate phase appears within the temperature range 4.7 - 5.1 K characterized by the propagation vector k2 = (kx, 0, kz) with kx/kz = 2. This ratio is reminiscent of the multiferroic phase of the orthorhombic RMnO3 phases (R = rare earth). This suggests that RbMnPO4 could present some multiferroic properties at low temperature. Our density functional calculations confirm the presence of magnetic frustration, which explains this intermediate incommensurate phase. Taking into account the strongest magnetic interactions, we are able to reproduce the magnetic structure observed experimentally at low temperature.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Nenert, Gwilherm and Bettis, Jerry, Jr. and Kremer, Reinhard and Ben Yahia, Hamdi and Ritter, Clemens and Gaudin, Etienne and Isnard, Olivier and Whangbo, Myung-Hwan}, year={2013}, month={Aug}, pages={9627–9635} }
 @article{ma_liu_collins_wang_bao_xu_enriquez_chen_lin_whangbo_2013, title={Magnetic and Electrical Transport Properties of LaBaCo2O5.5+delta Thin Films on Vicinal (001) SrTiO3 Surfaces}, volume={5}, ISSN={["1944-8252"]}, DOI={10.1021/am302553y}, abstractNote={Highly epitaxial LaBaCo2O5.5+δ thin films were grown on the vicinal (001) SrTiO3 substrates with miscut angles of 0.5°, 3.0°, and 5.0° to systemically study strain effect on its physical properties. The electronic transport properties and magnetic behaviors of these films are strongly dependent on the miscut angles. With increasing the miscut angle, the transport property of the film changes from semiconducting to semimetallic, which results most probably from the locally strained domains induced by the surface step terraces. In addition, a very large magnetoresistance (34% at 60 K) was achieved for the 0.5°-miscut film, which is ∼30% larger than that for the film grown on the regular (001) SrTiO3 substrates.}, number={2}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ma, Chunrui and Liu, Ming and Collins, Gregory and Wang, Haibin and Bao, Shanyong and Xu, Xing and Enriquez, Erik and Chen, Chonglin and Lin, Yuan and Whangbo, Myung-Hwan}, year={2013}, month={Jan}, pages={451–455} }
 @article{xiang_lee_koo_gong_whangbo_2013, title={Magnetic properties and energy-mapping analysis}, volume={42}, ISSN={["1477-9234"]}, DOI={10.1039/c2dt31662e}, abstractNote={The magnetic energy levels of a given magnetic solid are closely packed in energy because the interactions between magnetic ions are weak. Thus, in describing its magnetic properties, one needs to generate its magnetic energy spectrum by employing an appropriate spin Hamiltonian. In this review article we discuss how to determine and specify a necessary spin Hamiltonian in terms of first principles electronic structure calculations on the basis of energy-mapping analysis and briefly survey important concepts and phenomena that one encounters in reading the current literature on magnetic solids. Our discussion is given on a qualitative level from the perspective of magnetic energy levels and electronic structures. The spin Hamiltonian appropriate for a magnetic system should be based on its spin lattice, i.e., the repeat pattern of its strong magnetic bonds (strong spin exchange paths), which requires one to evaluate its Heisenberg spin exchanges on the basis of energy-mapping analysis. Other weaker energy terms such as Dzyaloshinskii–Moriya (DM) spin exchange and magnetocrystalline anisotropy energies, which a spin Hamiltonian must include in certain cases, can also be evaluated by performing energy-mapping analysis. We show that the spin orientation of a transition-metal magnetic ion can be easily explained by considering its split d-block levels as unperturbed states with the spin–orbit coupling (SOC) as perturbation, that the DM exchange between adjacent spin sites can become comparable in strength to the Heisenberg spin exchange when the two spin sites are not chemically equivalent, and that the DM interaction between rare-earth and transition-metal cations is governed largely by the magnetic orbitals of the rare-earth cation.}, number={4}, journal={DALTON TRANSACTIONS}, author={Xiang, Hongjun and Lee, Changhoon and Koo, Hyun-Joo and Gong, Xingao and Whangbo, Myung-Hwan}, year={2013}, pages={823–853} }
 @article{guguchia_caslin_kremer_keller_shengelaya_maisuradze_bettis_kohler_bussmann-holder_whangbo_2013, title={Nonlinear pressure dependence of T-N in almost multiferroic EuTiO3}, volume={25}, number={37}, journal={Journal of Physics. Condensed Matter}, author={Guguchia, Z. and Caslin, K. and Kremer, R. K. and Keller, H. and Shengelaya, A. and Maisuradze, A. and Bettis, J. L. and Kohler, J. and Bussmann-Holder, A. and Whangbo, M. H.}, year={2013} }
 @article{hakouk_deniard_lajaunie_guillot-deudon_harel_wang_huang_koo_whangbo_jobic_et al._2013, title={Novel Soft-Chemistry Route of Ag2Mo3O10 center dot 2H(2)O Nanowires and in Situ Photogeneration of a Ag@Ag2Mo3O10 center dot 2H(2)O Plasmonic Heterostructure}, volume={52}, ISSN={["1520-510X"]}, DOI={10.1021/ic400343v}, abstractNote={Ultrathin Ag2Mo3O10·2H2O nanowires (NWs) were synthesized by soft chemistry under atmospheric pressure from a hybrid organic–inorganic polyoxometalate (CH3NH3)2[Mo7O22] and characterized by powder X-ray diffraction, DSC/TGA analyses, FT-IR and FT-Raman spectroscopies, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Their diameters are a few tens of nanometers and hence much thinner than that found for silver molybdates commonly obtained under hydrothermal conditions. The optical properties of Ag2Mo3O10·2H2O NWs before and after UV irradiation were investigated by UV–vis–NIR diffuse reflectance spectroscopy revealing, in addition to photoreduction of Mo6+ to Mo5+ cations, in situ photogeneration of well-dispersed silver Ag0 nanoparticles on the surface of the NWs. The resulting Ag@Ag2Mo3O10·2H2O heterostructure was confirmed by electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), and Auger spectroscopy. Concomitant reduction of Mo6+ and Ag+ cations under UV excitation was discussed on the basis of electronic band structure calculations. The Ag@Ag2Mo3O10·2H2O nanocomposite is an efficient visible-light-driven plasmonic photocatalyst for degradation of Rhodamine B dye in aqueous solution.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Hakouk, Khadija and Deniard, Philippe and Lajaunie, Luc and Guillot-Deudon, Catherine and Harel, Sylvie and Wang, Zeyan and Huang, Baibiao and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Jobic, Stephane and et al.}, year={2013}, month={Jun}, pages={6440–6449} }
 @article{kasapbasi_whangbo_2013, title={On the nature of the photochemical reaction of polypyridyl Ru(II) complexes leading to sunlight-to-chemical energy conversion: density functional analysis}, volume={3}, number={24}, journal={RSC Advances}, author={Kasapbasi, E. E. and Whangbo, M. H.}, year={2013}, pages={9414–9418} }
 @article{brinzari_chen_sun_liu_tung_wang_schlueter_singleton_manson_whangbo_et al._2013, title={Quantum Critical Transition Amplifies Magnetoelastic Coupling in Mn[N(CN)(2)](2)}, volume={110}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.110.237202}, abstractNote={We report the discovery of a magnetic quantum critical transition in $\mathrm{Mn}[\mathrm{N}(\mathrm{CN}{)}_{2}{]}_{2}$ that drives the system from a canted antiferromagnetic state to the fully polarized state with amplified magnetoelastic coupling as an intrinsic part of the process. The local lattice distortions, revealed through systematic phonon frequency shifts, suggest a combined ${\mathrm{MnN}}_{6}$ octahedra $\mathrm{\text{distortion}}+\mathrm{\text{counterrotation}}$ mechanism that reduces antiferromagnetic interactions and acts to accommodate the field-induced state. These findings deepen our understanding of magnetoelastic coupling near a magnetic quantum critical point and away from the static limit.}, number={23}, journal={PHYSICAL REVIEW LETTERS}, author={Brinzari, T. V. and Chen, P. and Sun, Q. -C. and Liu, J. and Tung, L. -C. and Wang, Y. and Schlueter, J. A. and Singleton, J. and Manson, J. L. and Whangbo, M. -H. and et al.}, year={2013}, month={Jun} }
 @article{bykov_zhang_schoenleber_woelfel_ali_smaalen_glaum_koo_whangbo_reuvekamp_et al._2013, title={Spin-Peierls distortions in TiPO4}, volume={88}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.88.184420}, abstractNote={On the basis of single-crystal x-ray diffraction we show that TiPO${}_{4}$ undergoes a spin-Peierls distortion below 74.5(5) K, with a dimerization of the Ti chains along the $\mathbf{c}$ axis. Between 74.5(5) and 111.6(3) K, TiPO${}_{4}$ develops an incommensurate (IC) phase with temperature-dependent $\mathbf{q}$ vector (${\ensuremath{\sigma}}_{1}$,0,0). Density functional calculations strongly suggest that the IC phase results from a frustration of the lock-in spin-Peierls transition due to the competition of three energetically almost degenerate crystal structures and elastic coupling of the Ti chains via the bridging PO${}_{4}$ units. The phase transition into the IC phase is of second order, but the lock-in transition into the spin-Peierls distortion below 74.5 K is of weak first order in nature.}, number={18}, journal={PHYSICAL REVIEW B}, author={Bykov, Maxim and Zhang, Jian and Schoenleber, Andreas and Woelfel, Alexander and Ali, Sk Imran and Smaalen, Sander and Glaum, R. and Koo, H. -J. and Whangbo, M. -H. and Reuvekamp, P. G. and et al.}, year={2013}, month={Nov} }
 @article{nalbandyan_zvereva_yalovega_shukaev_ryzhakova_guda_stroppa_picozzi_vasiliev_whangbo_2013, title={Synthesis and Characterization of MnCrO4, a New Mixed-Valence Antiferromagnet}, volume={52}, ISSN={["1520-510X"]}, DOI={10.1021/ic401391b}, abstractNote={A new orthorhombic phase, MnCrO4, isostructural with MCrO4 (M = Mg, Co, Ni, Cu, Cd) was prepared by evaporation of an aqueous solution, (NH4)2Cr2O7 + 2 Mn(NO3)2, followed by calcination at 400 °C. It is characterized by redox titration, Rietveld analysis of the X-ray diffraction pattern, Cr K edge and Mn K edge XANES, ESR, magnetic susceptibility, specific heat and resistivity measurements. In contrast to the high-pressure MnCrO4 phase where both cations are octahedral, the new phase contains Cr in a tetrahedral environment suggesting the charge balance Mn2+Cr6+O4. However, the positions of both X-ray absorption K edges, the bond lengths and the ESR data suggest the occurrence of some mixed-valence character in which the mean oxidation state of Mn is higher than 2 and that of Cr is lower than 6. Both the magnetic susceptibility and the specific heat data indicate an onset of a three-dimensional antiferromagnetic order at TN ≈ 42 K, which was confirmed also by calculating the spin exchange interactions on the basis of first principles density functional calculations. Dynamic magnetic studies (ESR) corroborate this scenario and indicate appreciable short-range correlations at temperatures far above TN. MnCrO4 is a semiconductor with activation energy of 0.27 eV; it loses oxygen on heating above 400 °C to form first Cr2O3 plus Mn3O4 and then Mn1.5Cr1.5O4 spinel.}, number={20}, journal={INORGANIC CHEMISTRY}, author={Nalbandyan, Vladimir B. and Zvereva, Elena A. and Yalovega, Galina E. and Shukaev, Igor L. and Ryzhakova, Anastasiya P. and Guda, Alexander A. and Stroppa, Alessandro and Picozzi, Silvia and Vasiliev, Alexander N. and Whangbo, Myung-Hwan}, year={2013}, month={Oct}, pages={11850–11858} }
 @article{niu_dai_guo_ma_huang_whangbo_2013, title={Tunable topological surface and realization of insulating massive Dirac fermion state in Bi2Te2Se with co-substitution}, volume={1}, ISSN={["2050-7534"]}, DOI={10.1039/c2tc00017b}, abstractNote={The ternary topological insulator Bi2Te2Se is exceptional as it has a larger bulk resistivity than previously studied topological insulators. Here we explored the possibility of modifying the topological surface states and achieving the insulating massive Dirac fermion state in Bi2Te2Se on the basis of density functional calculations. Substitution of O for the outmost-layer Te leads to tunable surface states with an ideal Dirac cone. The co-substitution of Cr and O, as well as that of Mn and F, for the surface Bi and Te places the Dirac point inside the bulk band gap and opens a band gap at the Dirac point, hence creating the insulating massive Dirac fermion state. The co-substitution of magnetic and non-magnetic elements is a promising way of tuning the properties of topological insulators.}, number={1}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Niu, Chengwang and Dai, Ying and Guo, Meng and Ma, Yandong and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2013}, pages={114–120} }
 @article{xiang_wang_whangbo_gong_2013, title={Unified model of ferroelectricity induced by spin order}, volume={88}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.88.054404}, abstractNote={For spin-order-driven ferroelectricity, a general theory that includes both purely electronic and ion-displacement contributions simultaneously is lacking. Here we present a realistic method for describing the ion-displacement part of the ferroelectricity and combine it with the pure electronic description proposed earlier to formulate a unified model that can describe any spin order including an incommensurate one. This unified model reproduces first-principles results known for representative multiferroics and provides insight into the origin of ferroelectricity and magnetoelectric coupling. We find that multiferroicity in spiral magnets LiCuVO${}_{4}$ and TbMnO${}_{3}$ can be explained by our unified model, but not by previous spin current models. The magnetoelectric effect observed for BiFeO${}_{3}$ in the cycloidal spiral state is found to originate from the exchange striction.}, number={5}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Wang, P. S. and Whangbo, M. -H. and Gong, X. G.}, year={2013}, month={Aug} }
 @article{koo_whangbo_2012, title={Analysis of the magnetic structure of the manganese oxychalcogenides R2Mn2Se2O (R=LaO, BaF) by density functional calculations}, volume={324}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2012.06.035}, abstractNote={We examined the magnetic structures of R2Mn2Se2O (R=LaO, BaF) by evaluating the spin exchange interactions on the basis of density functional theory (DFT) calculations, and compared how they differ from that of the Fe analog (BaF)2Fe2Se2O. In R2Mn2Se2O (R=LaO, BaF), the two-dimensional antiferromagnetic square lattice defined by J1 is spin-frustrated, and the exchange J1 is stronger for (LaO)2Mn2Se2O than for (BaF)2Mn2Se2O by a factor of 1.5 explaining why the magnetic susceptibility maximum occurs at a higher temperature for (LaO)2Mn2Se2O than for (BaF)2Mn2Se2O (360 vs. 210 K). We identified two probable reasons why the specific heat anomaly at the long-range antiferromagnetic ordering temperature TN is significantly weaker for R2Mn2Se2O than for (BaF)2Fe2Se2O.}, number={22}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2012}, month={Nov}, pages={3859–3862} }
 @article{zhao_hung_li_chen_wu_kremer_banks_simon_whangbo_lee_et al._2012, title={CuBr2-A New Multiferroic Material with High Critical Temperature}, volume={24}, ISSN={["0935-9648"]}, DOI={10.1002/adma.201200734}, abstractNote={A new multiferroic material, CuBr2, is reported for the first time. CuBr2 has not only a high transition temperature (close to liquid nitrogen temperature) but also low dielectric loss and strong magnetoelectric coupling. These findings reveal the importance of anion effects in the search for the high temperature multiferroics materials among these low-dimensional spin systems.}, number={18}, journal={ADVANCED MATERIALS}, author={Zhao, Li. and Hung, Tsu-Lien and Li, Ching-Chien and Chen, Yang-Yuan and Wu, Maw-Kuen and Kremer, Reinhard K. and Banks, Michael G. and Simon, Arndt and Whangbo, Myung-Hwan and Lee, Changhoon and et al.}, year={2012}, month={May}, pages={2469–2473} }
 @article{kasapbasi_whangbo_2012, title={Density Functional Investigation of the Water Oxidation by Iron Complexes Based on Tetradentate Nitrogen Ligands}, volume={51}, ISSN={["1520-510X"]}, DOI={10.1021/ic3013359}, abstractNote={Recently it was discovered that the iron coordination complex LN4Fe(II)(OTf)2 (1) (LN4 = neutral tetraazadendate ligand and OTf = OSO2CF3) and its analogues are efficient water oxidizing catalysts (WOCs) in aqueous acidic solution with excess amount of ceric(IV) ammonium nitrate (CAN), [Ce(IV)(NO3)6](NH4)2, as sacrificial oxidants. The probable mechanism of water oxidation by these catalysts was explored on the basis of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations for 1 as a representative WOC. We examined the conversion of 1 to the resting intermediate [LN4Fe(IV)(O)(OH2)]2+ [2(IV)] as well as two catalytic cycles involving 2(IV): one proposed by Fillol et al. [Nat. Chem. 2011, 3, 1] in which the Fe oxidation states of the intermediate species vary from +2 to +5, and the alternative cycle in which they remain constant at +4. In addition, we investigated the role of the sacrificial oxidant CAN in driving the catalytic cycle. Our DFT and TD-DFT calculations confirm the experimental observation that 2(IV) is the resting species, and indicate that the catalytic cycle in which the Fe oxidation states of the intermediate species remain at +4 is energetically more favorable.}, number={20}, journal={INORGANIC CHEMISTRY}, author={Kasapbasi, Esra E. and Whangbo, Myung-Hwan}, year={2012}, month={Oct}, pages={10850–10855} }
 @article{koo_lee_whangbo_2012, title={Density functional analysis of the magnetic structures of Sr2MGe2O7 (M = Mn, Co)}, volume={324}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2012.06.001}, abstractNote={Abstract To examine the difference between the magnetic structures of Sr2MGe2O7 (M=Mn, Co), we evaluated their spin exchange interactions by performing energy-mapping analysis based on density functional theory calculations. The calculated intra- and inter-layer spin exchanges correctly predict the G-type and C-type antiferromagnetic structures of Sr2MnGe2O7 and Sr2CoGe2O7, respectively, and the Curie–Weiss temperatures estimated from these spin exchanges are also in good agreement with the experiment. The ∥c and ⊥c orientations of the spins in the ordered magnetic structures of Sr2MnGe2O7 and Sr2CoGe2O7, respectively, were also examined by considering spin–orbit coupling.}, number={22}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Koo, Hyun-Joo and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2012}, month={Nov}, pages={3716–3718} }
 @article{lu_whangbo_dong_gong_xiang_2012, title={Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined Effect of Dzyaloshinskii-Moriya Interaction and Exchange Striction}, volume={108}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.108.187204}, abstractNote={By extending our general spin-current model to non-centrosymmetric spin dimers and performing density functional calculations, we investigate the causes for the helical magnetic order and the origin of the giant ferroelectric polarization of CaMn7O12. The giant ferroelectric polarization is proposed to be caused by the symmetric exchange striction due to the canting of the Mn4+ spin arising from its strong Dzyaloshinskii-Moriya (DM) interaction. Our study suggests that CaMn7O12 may exhibit a novel magnetoelectric coupling mechanism in which the magnitude of the polarization is governed by the exchange striction, but the direction of the polarization by the chirality of the helical magnetic order.}, number={18}, journal={PHYSICAL REVIEW LETTERS}, author={Lu, X. Z. and Whangbo, M. -H. and Dong, Shuai and Gong, X. G. and Xiang, H. J.}, year={2012}, month={May} }
 @article{liu_ma_liu_collins_chen_he_jiang_meletis_sun_jacobson_et al._2012, title={Giant Magnetoresistance and Anomalous Magnetic Properties of Highly Epitaxial Ferromagnetic LaBaCo2O5.5+delta Thin Films on (001) MgO}, volume={4}, ISSN={["1944-8244"]}, DOI={10.1021/am301427c}, abstractNote={Ferromagnetic thin films of the A-site nano-ordered double perovskite LaBaCo2O5.5+δ (LBCO) were grown on (001) MgO, and their structural and magnetic properties were characterized. The as-grown films have an excellent epitaxial behavior with atomically sharp interfaces, with the c-axis of the LBCO structure lying in the film plane and the interface relationship given by (100)LBCO//(001)MgO and [001]LBCO//[100]MgO or [010]MgO. The as-grown LBCO films exhibit a giant magnetoresistance (54% at 40 K under 7 T) and an anomalous magnetic hysteresis, depending strongly on the temperature and the applied magnetic field scan width.}, number={10}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Liu, Ming and Ma, Chunrui and Liu, Jian and Collins, Gregory and Chen, Chonglin and He, Jie and Jiang, Jiechao and Meletis, Efstathios I. and Sun, Li and Jacobson, Allan J. and et al.}, year={2012}, month={Oct}, pages={5524–5528} }
 @article{li_whangbo_gong_xiang_2012, title={Helicoidal magnetic structure and ferroelectric polarization in Cu3Nb2O8}, volume={86}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.86.174401}, abstractNote={We investigate the origin of the coplanar helicoidal magnetic structure and the ferroelectric polarization in Cu3Nb2O8 by combining first-principles calculations and our spin-induced ferroelectric polarization model. The coplanar helicoidal spin state comes from the competition between the isotropic exchange interactions, and the ferroelectric polarization from the symmetric exchange striction with slight spin canting. However, the direction of the polarization is not determined by the orientation of the spin rotation plane.}, number={17}, journal={PHYSICAL REVIEW B}, author={Li, Zheng-Lu and Whangbo, M. -H. and Gong, X. G. and Xiang, H. J.}, year={2012}, month={Nov} }
 @article{zheng_huang_lu_wang_qin_zhang_dai_whangbo_2012, title={Hydrogenated titania: synergy of surface modification and morphology improvement for enhanced photocatalytic activity}, volume={48}, number={46}, journal={Chemical Communications}, author={Zheng, Z. K. and Huang, B. B. and Lu, J. B. and Wang, Z. Y. and Qin, X. Y. and Zhang, X. Y. and Dai, Y. and Whangbo, M. H.}, year={2012}, pages={5733–5735} }
 @article{schlueter_park_halder_armand_dunmars_chapman_manson_singleton_mcdonald_plonczak_et al._2012, title={Importance of Halogen center dot center dot center dot Halogen Contacts for the Structural and Magnetic Properties of CuX2(pyrazine-N,N '-dioxide)(H2O)(2) (X = Cl and Br)}, volume={51}, number={4}, journal={Inorganic Chemistry}, author={Schlueter, J. A. and Park, H. and Halder, G. J. and Armand, W. R. and Dunmars, C. and Chapman, K. W. and Manson, J. L. and Singleton, J. and McDonald, R. and Plonczak, A. and et al.}, year={2012}, pages={2121–2129} }
 @article{meddar_josse_maglione_guiet_la_deniard_decourt_lee_tian_jobic_et al._2012, title={Increasing the Phase-Transition Temperatures in Spin-Frustrated Multiferroic MnWO4 by Mo Doping}, volume={24}, ISSN={["1520-5002"]}, DOI={10.1021/cm2031653}, abstractNote={Ceramic samples of MnW1–xMoxO4 (x ≤ 0.3) solid solution were prepared by a solid-state route with the goal of increasing the magnitude of the spin-exchange couplings among the Mn2+ ions in the spin spiral multiferroic MnWO4. Samples were characterized by X-ray diffraction, optical spectroscopy, magnetization, and dielectric permittivity measurements. It was observed that the Néel temperature TN, the spin spiral ordering temperature TM2, and the ferroelectric phase-transition temperature TFE2 of MnWO4 increased upon the nonmagnetic substitution of Mo6+ for W6+. Like pure MnWO4, the ferroelectric critical temperature TFE2(x) coincides with the magnetic ordering temperature TM2(x). A density functional analysis of the spin-exchange interactions for a hypothetical MnMoO4 that is isostructural with MnWO4 suggests that Mo substitution increases the strength of the spin-exchange couplings among Mn2+ in the vicinity of a Mo6+ ion. Our study shows that the Mo-doped MnW1–xMoxO4 (x ≤ 0.3) compounds are spin-frustrated materials that have higher magnetic and ferroelectric phase-transition temperatures than does pure MnWO4.}, number={2}, journal={CHEMISTRY OF MATERIALS}, author={Meddar, Lynda and Josse, Michael and Maglione, Mario and Guiet, Amandine and La, Carole and Deniard, Philippe and Decourt, Rodolphe and Lee, Changhoon and Tian, Chuan and Jobic, Stephane and et al.}, year={2012}, month={Jan}, pages={353–360} }
 @article{manson_carreiro_lapidus_stephens_goddard_del sesto_bendix_ghannadzadeh_franke_singleton_et al._2012, title={Influence of HF2- geometry on magnetic interactions elucidated from polymorphs of the metal-organic framework [Ni(HF2)(pyz)(2)]PF6 (pyz = pyrazine)}, volume={41}, number={24}, journal={Dalton Transactions (Cambridge, England : 2003)}, author={Manson, J. L. and Carreiro, K. E. and Lapidus, S. H. and Stephens, P. W. and Goddard, P. A. and Del Sesto, R. E. and Bendix, J. and Ghannadzadeh, S. and Franke, I. and Singleton, J. and et al.}, year={2012}, pages={7235–7243} }
 @article{lee_liu_whangbo_koo_kremer_simon_2012, title={Investigation of the spin exchange interactions and the magnetic structure of the high-temperature multiferroic CuBr2}, volume={86}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.86.060407}, abstractNote={We report a detailed density functional analysis of the spin exchange interactions and the magnetic structure of the high-temperature multiferroic CuBr${}_{2}$ and compare the results with magnetic susceptibility measurements. CuBr${}_{2}$ shows one-dimensional antiferromagnetism and undergoes long-range antiferromagnetic ordering at $\ensuremath{\sim}$74 K. Due to the competition between the nearest- and next-nearest-neighbor spin exchanges, each Cu${}^{2+}$ chain has a cycloidal spin-spiral structure, which is described approximately by a quadrupling of the nuclear cell with spin moment rotation of $\ensuremath{\sim}$${85}^{\ensuremath{\circ}}$ in the plane of the CuBr${}_{2}$ ribbon plane.}, number={6}, journal={PHYSICAL REVIEW B}, author={Lee, C. and Liu, Jia and Whangbo, M. -H. and Koo, H. -J. and Kremer, R. K. and Simon, A.}, year={2012}, month={Aug} }
 @article{koo_kremer_whangbo_2012, title={Non-idle-spin behavior and field-induced magnetic transitions of the triple chain magnet Cu-3(OH)(4)SO4}, volume={81}, number={6}, journal={Journal of the Physical Society of Japan}, author={Koo, H. J. and Kremer, R. K. and Whangbo, M. H.}, year={2012} }
 @article{tong_koehler_simon_lee_whangbo_2012, title={Optical Properties of the Orchid Colored Silver(II) Fluoride Cs2AgF4}, volume={638}, ISSN={["0044-2313"]}, DOI={10.1002/zaac.201200315}, abstractNote={Abstract Orchid colored powder samples of Cs 2 AgF 4 were prepared by a solid state reaction from CsF and AgF 2 . The diffuse reflectance spectrum of a powder sample of Cs 2 AgF 4 was measured in the UV/Vis region. It shows three broad bands, two in the visible‐light region at 650 nm, 500 nm and one in the UV region at 259 nm. The bands are assigned to F 2p → Ag 4d and Ag 4d → Ag 4d transitions. The optical band gap for Cs 2 AgF 4 determined from the UV/Vis diffuse reflectance spectrum is approx. 2.17 eV. In order to interpret the observed absorptions, the theoretical absorption spectrum of Cs 2 AgF 4 was obtained from density functional calculations.}, number={11}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Tong, Jianwei and Koehler, Juergen and Simon, Arndt and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2012}, month={Sep}, pages={1792–1795} }
 @article{wang_huang_dai_whangbo_2012, title={Plasmonic photocatalysts: Harvesting visible light with noble metal nanoparticles}, volume={14}, number={28}, journal={Physical Chemistry Chemical Physics}, author={Wang, P. and Huang, B. B. and Dai, Y. and Whangbo, M. H.}, year={2012}, pages={9813–9825} }
 @article{lee_kan_xiang_kremer_lee_hiroi_whangbo_2012, title={Spin Reorientation in the Square-Lattice Antiferromagnets RMnAsO (R = Ce, Nd): Density Functional Analysis of the Spin-Exchange Interactions between the Rare-Earth and Transition-Metal Ions}, volume={51}, ISSN={["1520-510X"]}, DOI={10.1021/ic300685d}, abstractNote={The spin reorientation (SR) phenomenon of the square-lattice antiferromagnets RMnAsO (R = Ce, Nd) was investigated by analyzing the spin-exchange interactions between the rare-earth and the transition-metal ions (R3+ and Mn2+, respectively) on the basis of density functional calculations. It is found that the symmetry and strength of the Dzyaloshinskii–Moriya (DM) interaction are determined primarily by the partially filled 4f states of the R3+ ions and that the DM and biquadratic (BQ) exchanges between the R3+ and the Mn2+ ions are unusually strong and control the observed spin reorientation phenomenon. Below their SR temperature, the Mn2+ and Ce3+ moments are orthogonal in CeMnAsO but are collinear in NdMnAsO, because the DM interaction dominates over the BQ interaction for CeMnAsO, while the opposite is the case for NdMnAsO. Experiments designed to test the implications of our findings are proposed.}, number={12}, journal={INORGANIC CHEMISTRY}, author={Lee, Changhoon and Kan, Erjun and Xiang, Hongjun and Kremer, Reinhard K. and Lee, Seung-Hun and Hiroi, Zenji and Whangbo, Myung-Hwan}, year={2012}, month={Jun}, pages={6890–6897} }
 @article{lee_kan_whangbo_bussmann-holder_simon_2012, title={Spin/Charge Redistributions and Oxygen Atom Displacements Induced by Spin Flip and Hole Doping in the CuO2 Layer of High-Temperature Superconductors}, volume={25}, ISSN={["1557-1939"]}, DOI={10.1007/s10948-011-1208-3}, number={1}, journal={JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM}, author={Lee, C. and Kan, E. J. and Whangbo, M. -H. and Bussmann-Holder, A. and Simon, A.}, year={2012}, month={Jan}, pages={55–59} }
 @article{yang_li_lu_whangbo_wei_gong_xiang_2012, title={Strong Dzyaloshinskii-Moriya Interaction and Origin of Ferroelectricity in Cu2OSeO3}, volume={109}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.109.107203}, abstractNote={By performing density functional calculations, we investigate the origin of the skyrmion state and ferroelectricity in Cu2OSeO3. We find that the Dzyaloshinskii-Moriya interactions between the two different kinds of Cu ions are extremely strong and induce the helical ground state and the skyrmion state in the absence and presence of magnetic field, respectively. On the basis of the general model for the spin-order induced polarization, we propose that the ferroelectric polarization of Cu2OSeO3 in the collinear ferrimagnetic state arises from an unusual mechanism, i.e., the single-spin-site contribution due to the spin-orbit coupling.}, number={10}, journal={PHYSICAL REVIEW LETTERS}, author={Yang, J. H. and Li, Z. L. and Lu, X. Z. and Whangbo, M. -H. and Wei, Su-Huai and Gong, X. G. and Xiang, H. J.}, year={2012}, month={Sep} }
 @article{ben yahia_shikano_koike_tatsumi_kobayashi_kawaji_avdeev_miiller_ling_liu_et al._2012, title={Synthesis and characterization of the crystal structure and magnetic properties of the new fluorophosphate LiNaCo[PO4]F}, volume={51}, DOI={10.1021/ic300374w}, abstractNote={The new compound LiNaCo[PO(4)]F was synthesized by a solid state reaction route, and its crystal structure was determined by single-crystal X-ray diffraction measurements. The magnetic properties of LiNaCo[PO(4)]F were characterized by magnetic susceptibility, specific heat, and neutron powder diffraction measurements and also by density functional calculations. LiNaCo[PO(4)]F crystallizes with orthorhombic symmetry, space group Pnma, with a = 10.9334(6), b = 6.2934(11), c = 11.3556(10) Å, and Z = 8. The structure consists of edge-sharing CoO(4)F(2) octahedra forming CoFO(3) chains running along the b axis. These chains are interlinked by PO(4) tetrahedra forming a three-dimensional framework with the tunnels and the cavities filled by the well-ordered sodium and lithium atoms, respectively. The magnetic susceptibility follows the Curie-Weiss behavior above 60 K with θ = -21 K. The specific heat and magnetization measurements show that LiNaCo[PO(4)]F undergoes a three-dimensional magnetic ordering at T(mag) = 10.2(5) K. The neutron powder diffraction measurements at 3 K show that the spins in each CoFO(3) chain along the b-direction are ferromagnetically coupled, while these FM chains are antiferromagnetically coupled along the a-direction but have a noncollinear arrangement along the c-direction. The noncollinear spin arrangement implies the presence of spin conflict along the c-direction. The observed magnetic structures are well explained by the spin exchange constants determined from density functional calculations.}, number={16}, journal={Inorganic Chemistry}, author={Ben Yahia, H. and Shikano, M. and Koike, S. and Tatsumi, K. and Kobayashi, H. and Kawaji, H. and Avdeev, M. and Miiller, W. and Ling, C. D. and Liu, J. and et al.}, year={2012}, pages={8729–8738} }
 @article{zhang_dai_yu_guo_huang_whangbo_2012, title={The surface termination effect on the quantum confinement and electron affinities of 3C-SiC quantum dots: a first-principles study}, volume={4}, number={5}, journal={Nanoscale}, author={Zhang, Z. K. and Dai, Y. and Yu, L. and Guo, M. and Huang, B. B. and Whangbo, M. H.}, year={2012}, pages={1592–1597} }
 @article{kim_kim_rhee_kim_whangbo_2012, title={Tip-Induced Modification of Polyoxometalate-Dodecane Thiol Self-Assembled Monolayers on Au(111) during Scanning Tunneling Microscopy Imaging}, volume={33}, ISSN={["0253-2964"]}, DOI={10.5012/bkcs.2012.33.9.3139}, abstractNote={Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USAReceived June 14, 2012, Accepted June 26, 2012Key Words : Au(111), Polyoxometalate, Self-assembled monolayer, Dodecanethiol, Scanning tunneling mi-croscopySelf-assembled monolayers (SAMs) of thiolates on Ausurfaces have been extensively investigated for the last fewdecades because such systems offer useful applications inthe field of nanoscience and nanotechnology.}, number={9}, journal={BULLETIN OF THE KOREAN CHEMICAL SOCIETY}, author={Kim, Jandee and Kim, Hyeran and Rhee, Choong Kyun and Kim, Jongwon and Whangbo, Myung Hwan}, year={2012}, month={Sep}, pages={3139–3141} }
 @article{manson_baldwin_scott_bendix_del sesto_goddard_kohama_tran_ghannadzadeh_singleton_et al._2012, title={[Ni(HF2)(3-Clpy)(4)]BF4 (py = pyridine): Evidence for spin exchange along strongly distorted F center dot center dot center dot H center dot center dot center dot F- bridges in a one-dimensional polymeric chain}, volume={51}, number={14}, journal={Inorganic Chemistry}, author={Manson, J. L. and Baldwin, A. G. and Scott, B. L. and Bendix, J. and Del Sesto, R. E. and Goddard, P. A. and Kohama, Y. and Tran, H. E. and Ghannadzadeh, S. and Singleton, J. and et al.}, year={2012}, pages={7520–7528} }
 @article{tsukamoto_okamoto_matsuhira_whangbo_hiroi_2011, title={A magnetic transition probed by the Ce ion in square-lattice antiferromagnet CeMnAsO}, volume={80}, number={9}, journal={Journal of the Physical Society of Japan}, author={Tsukamoto, Y. and Okamoto, Y. and Matsuhira, K. and Whangbo, M. H. and Hiroi, Z.}, year={2011} }
 @article{zhao_nellutla_son_vaughn_ye_smith_caignaert_lufaso_pekarek_smirnov_et al._2011, title={Ba4KFe3O9: A Novel Ferrite Containing Discrete 6-Membered Rings of Corner-Sharing FeO4 Tetrahedra}, volume={50}, ISSN={["1520-510X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80053934262&partnerID=MN8TOARS}, DOI={10.1021/ic201374g}, abstractNote={Single crystals of a new iron-containing oxide, Ba(4)KFe(3)O(9), were grown from a hydroxide melt, and the crystal structure was determined by single-crystal X-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-membered rings of corner-sharing FeO(4) tetrahedra. Mössbauer measurements are indicative of two tetrahedral high-spin Fe(3+) coordination environments. The observed magnetic moment (~3.9 μ(B)) at 400 K is significantly lower than the calculated spin-only (~5.2 μ(B)) value, indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional theory calculations confirm the strong antiferromagnetic coupling between adjacent Fe(3+) sites within each 6-membered ring and estimate the nearest-neighbor spin-exchange integral as ~200 K; next-nearest-neighbor interactions are shown to be negligible. The lower than expected effective magnetic moment for Ba(4)KFe(3)O(9) calculated from χT data is explained as resulting from the occupation of lower-lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of a powder sample consist of a single line at g ~ 2.01 that is characteristic of Fe(3+) ions in a tetrahedral environment, thus confirming the Mössbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe(6) magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g factors but differ in their peak-to-peak line widths (δB(pp)). The line-width ratio δB(pp)(major)/δB(pp)(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θ(minor)/θ(major) ~ 4.}, number={20}, journal={INORGANIC CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Zhao, Qingbiao and Nellutla, Saritha and Son, Won-Joon and Vaughn, Shae A. and Ye, Longfei and Smith, Mark D. and Caignaert, Vincent and Lufaso, Michael and Pekarek, Thomas M. and Smirnov, Alex I. and et al.}, year={2011}, month={Oct}, pages={10310–10318} }
 @article{son_manuel_adroja_whangbo_2011, title={Density Functional Analysis of the Magnetic Structure of Li3RuO4: Importance of the Ru-O center dot center dot center dot O-Ru Spin-Exchange Interactions and Substitutional Ru Defects at the Li Sites}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic201023j}, abstractNote={We evaluated the spin-exchange interactions of Li3RuO4 by performing energy-mapping analysis based on density functional calculations and examined the nature of its magnetic transition at T1 = 66 K and the divergence of the field-cooled and zero-field-cooled susceptibilities below T2 = 32 K. Our study shows that T1 is associated with a three-dimensional antiferromagnetic ordering, in which the two-dimensional antiferromagnetic lattices parallel to the ab plane are antiferromagnetically coupled along the c direction. We examined how the substitutional defects, Ru atoms residing in the Li sites, affect the antiferromagnetic coupling along the c direction to explain why the expected c-axis doubling is not detected from powder neutron diffraction measurements. The susceptibility divergence below T2 is attributed to a slight spin canting out of the ab plane.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Son, Won-Joon and Manuel, Pascal and Adroja, Devashibhai and Whangbo, Myung-Hwan}, year={2011}, month={Oct}, pages={9400–9405} }
 @article{zhang_whangbo_2011, title={Density Functional Analysis of the Spin Exchange Interactions and Charge Order Patterns in the Layered Magnetic Oxides YBaM2O5 (M = Mn, Fe, Co)}, volume={50}, ISSN={["0020-1669"]}, DOI={10.1021/ic200963g}, abstractNote={The spin and charge order phenomena of the layered magnetic oxides YBaM2O5 (M = Mn, Fe, Co) were analyzed on the basis of density functional calculations. We evaluated the spin exchange interactions of YBaM2O5 by performing energy-mapping analysis based on density functional calculations to find why they undergo a three-dimensional magnetic ordering at high temperature. We estimated the relative stabilities of the checkerboard and stripe charge order patterns of YBaM2O5 (M = Mn, Fe, Co) by optimizing their structures with density functional calculations to probe if the nature of the charge order pattern depends on whether their transition-metal ions are Jahn–Teller active.}, number={21}, journal={INORGANIC CHEMISTRY}, author={Zhang, Yuemei and Whangbo, Myung-Hwan}, year={2011}, month={Nov}, pages={10643–10647} }
 @article{zhang_kan_whangbo_2011, title={Density Functional Investigation of the Difference in the Magnetic Structures of the Layered Triangular Antiferromagnets CuFeO2 and AgCrO2}, volume={23}, ISSN={["1520-5002"]}, DOI={10.1021/cm2011567}, abstractNote={The layered triangular antiferromagnets CuFeO2 and AgCrO2 exhibit ferroelectric polarization when they adopt a helical spiral-spin magnetic structure. Application of magnetic field parallel to the c-axis or doping Fe sites with Al or Ga is necessary for CuFeO2 to have a helical spiral spin order. However, AgCrO2 adopts a helical spiral spin order in the absence of such extrinsic factors. A probable cause for this difference between the two systems was examined by evaluating the relative stabilities of their helical spiral and collinear spin structures on the basis of density functional calculations. In contrast to the case of AgCrO2, the collinear ↑↑↓↓ state is only slightly higher in energy than the helical spiral-spin state Qa+b in CuFeO2 so that extrinsic factors such as oxygen vacancy and applied magnetic field can influence whether CuFeO2 adopts the ↑↑↓↓ or Qa+b structure.}, number={18}, journal={CHEMISTRY OF MATERIALS}, author={Zhang, Yuemei and Kan, Erjun and Whangbo, Myung-Hwan}, year={2011}, month={Sep}, pages={4181–4185} }
 @article{zhang_kan_xiang_villesuzanne_whangbo_2011, title={Density Functional Theory Analysis of the Interplay between Jahn-Teller Instability, Uniaxial Magnetism, Spin Arrangement, Metal-Metal Interaction, and Spin-Orbit Coupling in Ca3CoMO6 (M = Co, Rh, Ir)}, volume={50}, ISSN={["0020-1669"]}, DOI={10.1021/ic1022278}, abstractNote={In the isostructural oxides Ca(3)CoMO(6) (M = Co, Rh, Ir), the CoMO(6) chains made up of face-sharing CoO(6) trigonal prisms and MO(6) octahedra are separated by Ca atoms. We analyzed the magnetic and electronic properties of these oxides on the basis of density functional theory calculations including on-site repulsion and spin-orbit coupling, and examined the essential one-electron pictures hidden behind results of these calculations. Our analysis reveals an intimate interplay between Jahn-Teller instability, uniaxial magnetism, spin arrangement, metal-metal interaction, and spin-orbit coupling in governing the magnetic and electronic properties of these oxides. These oxides undergo a Jahn-Teller distortion, but their distortions are weak, so that their trigonal-prism Co(n+) (n = 2, 3) ions still give rise to strong easy-axis anisotropy along the chain direction. As for the d-state split pattern of these ions, the electronic and magnetic properties of Ca(3)CoMO(6) (M = Co, Rh, Ir) are consistent with d(0) < (d(2), d(-2)) < (d(1), d(-1)) but not with (d(2), d(-2)) < d(0) < (d(1), d(-1)). The trigonal-prism Co(3+) ion in Ca(3)Co(2)O(6) has the L = 2 configuration (d(0))(1)(d(2), d(-2))(3)(d(1), d(-1))(2) because of the metal-metal interaction between adjacent Co(3+) ions in each Co(2)O(6) chain, which is mediated by their z(2) orbitals, and the spin-orbit coupling of the trigonal-prism Co(3+) ion. The spins in each CoMO(6) chain of Ca(3)CoMO(6) prefer the ferromagnetic arrangement for M = Co and Rh but the antiferromagnetic arrangement for M = Ir. The octahedral M(4+) ion of Ca(3)CoMO(6) has the (1a)(1)(1e)(4) configuration for M = Rh but the (1a)(2)(1e)(3) configuration for M = Ir, which arises from the difference in the spin-orbit coupling of the M(4+) ions and the Co···M metal-metal interactions.}, number={5}, journal={INORGANIC CHEMISTRY}, author={Zhang, Yuemei and Kan, Erjun and Xiang, Hongjun and Villesuzanne, Antoine and Whangbo, Myung-Hwan}, year={2011}, month={Mar}, pages={1758–1766} }
 @article{hoch_simon_lee_whangbo_koehler_2011, title={Density functional analysis of the electronic structure of Cs9InO4: Evidence for the presence of a Cs- anion}, volume={226}, ISSN={["2196-7105"]}, DOI={10.1524/zkri.2011.1371}, abstractNote={The complex oxoindate Cs9InO4, described by the electron counting (Cs+)8Cs—[(In3+)(O2–)4] + 2e−, consists of InO4 tetrahedra and Cs(Cs)16 clusters. In each Cs(Cs)16 cluster a Cs atom is located at the center of the (Cs)16 cage, and the Cs9 sublattice of Cs9InO4 is obtained from the face- and edge-sharing of the Cs(Cs)16 clusters. To examine the charge density distribution among the Cs atoms in each Cs(Cs)16 cluster, density functional calculations were carried out for Cs9InO4, and the results were analyzed. Our analysis indicates that, to a first approximation, the Cs atom located at the center of each Cs(Cs)16 is best described as Cs– anion.}, number={7}, journal={ZEITSCHRIFT FUR KRISTALLOGRAPHIE-CRYSTALLINE MATERIALS}, author={Hoch, Constantin and Simon, Arndt and Lee, Changhoon and Whangbo, Myung-Hwan and Koehler, Juergen}, year={2011}, pages={553–556} }
 @article{tong_kraus_koehler_simon_liu_whangbo_2011, title={Dimers of Ag2+ Ions - Synthesis and Characterization of the Quaternary Silver Fluoride Ag2ZnZr2F14 with [Ag2F7](3-) Units}, volume={637}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.201100129}, abstractNote={Abstract Deep blue‐violet colored powder samples of Ag 2 ZnZr 2 F 14 were synthesized by heating Zn(NO 3 ) 2 ·4H 2 O, Ag and ZrOCl 2 ·8H 2 O at 300 °C under fluorine atmosphere. The crystal structure of Ag 2 ZnZr 2 F 14 was refined from X‐ray powder diffraction data using the Rietveld method ( C 2/ m, a = 9.0206(1) Å, b = 6.6373(1) Å, c = 9.0563(1) Å, β = 90.44(1)°, Z = 2). The structure is derived from the isotypic Ag 3 Zr 2 F 14 by replacing only one of the two crystallographically different Ag 2+ ions with Zn 2+ ions, thus leading to discrete Ag 2 F 7 dimers. These dimers are connected via nearly linear Ag–F···F–Ag bridges with short F···F distances of 2.33 Å to form two‐legged ladders. Magnetic susceptibility measurements and density functional calculations show that the two Ag 2+ ions in each Ag 2 F 7 dimer are strongly coupled antiferromagnetically.}, number={9}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Tong, Jianwei and Kraus, Florian and Koehler, Juergen and Simon, Arndt and Liu, Jia and Whangbo, Myung-Hwan}, year={2011}, month={Jul}, pages={1118–1121} }
 @article{zheng_huang_qin_zhang_dai_whangbo_2011, title={Facile in situ synthesis of visible-light plasmonic photocatalysts M@TiO2 (M = Au, Pt, Ag) and evaluation of their photocatalytic oxidation of benzene to phenol}, volume={21}, number={25}, journal={Journal of Materials Chemistry}, author={Zheng, Z. K. and Huang, B. B. and Qin, X. Y. and Zhang, X. Y. and Dai, Y. and Whangbo, M. H.}, year={2011}, pages={9079–9087} }
 @article{wang_huang_wang_wang_cheng_zheng_qin_zhang_dai_whangbo_2011, title={Facile synthesis of Zn-rich (GaN)(1-x)(ZnO)(x) solid solutions using layered double hydroxides as precursors}, volume={21}, number={12}, journal={Journal of Materials Chemistry}, author={Wang, J. P. and Huang, B. B. and Wang, Z. Y. and Wang, P. and Cheng, H. F. and Zheng, Z. K. and Qin, X. Y. and Zhang, X. Y. and Dai, Y. and Whangbo, M. H.}, year={2011}, pages={4562–4567} }
 @article{xiang_kan_zhang_whangbo_gong_2011, title={General Theory for the Ferroelectric Polarization Induced by Spin-Spiral Order}, volume={107}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.107.157202}, abstractNote={The ferroelectric polarization of triangular-lattice antiferromagnets induced by helical spin-spiral order is not explained by any existing model of magnetic-order-driven ferroelectricity. We resolve this problem by developing a general theory for the ferroelectric polarization induced by spin-spiral order and then by evaluating the coefficients needed to specify the general theory on the basis of density functional calculations. Our theory correctly describes the ferroelectricity of triangular-lattice antiferromagnets driven by helical spin-spiral order, and incorporates known models of magnetic-order-driven ferroelectricity as special cases.}, number={15}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Kan, E. J. and Zhang, Y. and Whangbo, M. -H. and Gong, X. G.}, year={2011}, month={Oct} }
 @article{kan_wu_xiang_yang_whangbo_2011, title={Half-Metallic Dirac Point in B-Edge Hydrogenated BN Nanoribbons}, volume={115}, ISSN={["1932-7447"]}, DOI={10.1021/jp2015269}, abstractNote={The BN zigzag nanoribbons (BNZNRs) were examined by first-principles density functional calculations, including structural relaxation. The quantum confinement and edge effects of the BNZNRs produce a magnetic ground state. When the B-edge is hydrogenated, the BNZNRs possess a new state with a spin-resloved Dirac point Fermi surface, which paves a way to realizing spin-polarized massless carriers.}, number={35}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kan, Erjun and Wu, Fang and Xiang, Hongjun and Yang, Jinlong and Whangbo, Myung-Hwan}, year={2011}, month={Sep}, pages={17252–17254} }
 @article{zhao_darriet_whangbo_ye_stackhouse_loye_2011, title={Intriguing Interconnections Among Phase Transition, Magnetic Moment, and Valence Disproportionation in 2H-Perovskite Related Oxides}, volume={133}, ISSN={["1520-5126"]}, DOI={10.1021/ja209198b}, abstractNote={In this paper we report the crystal growth, structure determination, and magnetic properties of the 2H-perovskite related oxides, Sr5Co4O12 and Sr6Co5O15, as well as the charge disproportionation and associated phase transition of Sr5Co4O12. Sr5Co4O12 and Sr6Co5O15 are the (m = 2, n = 3) and (m = 1, n = 1) members of the A3m+3nA′nB3m+nO9m+6n family, respectively. Sr6Co5O15 crystallizes in the space group R32 with lattice parameters of a = 9.5020(10) Å and c = 12.379(8) Å. The structure solution shows that Sr6Co5O15 is isostructural with Sr6Rh5O15. Magnetic measurements do not indicate any long-range magnetic order, although the Weiss temperature of −248 K indicates the presence of dominant antiferromagnetic interactions. Sr5Co4O12 crystallizes in the space group P-3c1 with lattice parameters of a = 9.4705(10) Å and c = 20.063(5) Å at room temperature. The single crystal structure solution revealed that the cobalt ions in the trigonal prismatic sites of Sr5Co4O12 undergo a structural transition at ∼170 K, where the cobalt atoms are in the center of the trigonal prisms below this temperature and move partially toward the faces above this temperature. This structure transition is accompanied by a change in the magnetic moment of the oxide and can be related to a valence disproportionation of the cobalt ions and a concomitant Jahn–Teller distortion. In addition, specific heat, Seebeck coefficient, electric conductivity, and magnetic measurements as well as bond valence sum calculations were carried out for Sr5Co4O12. Sr5Co4O12 exhibits strong magnetic anisotropy but no long-range magnetic order.}, number={51}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Zhao, Qingbiao and Darriet, Jacques and Whangbo, Myung-Hwan and Ye, Longfei and Stackhouse, Chavis and Loye, Hans-Conrad}, year={2011}, month={Dec}, pages={20981–20994} }
 @misc{whangbo_lee_kohler_2011, title={Metal Anions in Metal-Rich Compounds and Polar Intermetallics}, number={26}, journal={European Journal of Inorganic Chemistry}, author={Whangbo, M. H. and Lee, C. and Kohler, J.}, year={2011}, pages={3841–3847} }
 @article{manuel_adroja_lindgard_hillier_battle_son_whangbo_2011, title={Neutron scattering and mu SR investigations of quasi-one-dimensional magnetism in the spin=3/2 compound Li3RuO4}, volume={84}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.84.174430}, abstractNote={The $S$ = 3/2, quasi-one-dimensional (1D) zig-zag chain Heisenberg antiferromagnet Li${}_{3}$RuO${}_{4}$ has been investigated using heat capacity, inelastic neutron scattering, neutron diffraction, and \ensuremath{\mu}SR measurements on a powder sample. Our neutron diffraction and \ensuremath{\mu}SR studies confirm a long-range ordering of the magnetic moments on the Ru${}^{5+}$ cations below 40 K. The magnetic excitations were measured at various temperatures above and below the three-dimensional (3D) ordering temperature in order to understand the broad peak observed in the temperature dependence of the magnetic susceptibility. At 5 K we have observed two well-defined magnetic excitations at 5.5 meV and 8.5 meV and a weak low-energy peak near \ensuremath{\sim}2 meV. We interpret the 5.5 meV energy peak as a 1D zone-boundary mode and that at 8.5 meV as arising from a maximum away from the zone boundary in the dispersion curve for spin-wave modes along the chain of Ru${}^{5+}$ ions. The weaker peak near 2 meV is thought to arise from a weak interchain coupling. Our data are best reproduced using a model with three intrachain interactions and one weak interchain interaction. The experimental spin-exchange interactions are in good agreement with those calculated for a 1D model by density functional theory (DFT) methods. Furthermore, above ${T}_{N}$ we observe strong diffuse scattering at the same $Q$-position as the 5.5 meV mode, which suggests the presence of short-range magnetic correlations above ${T}_{N}$. We have estimated the correlation length \ensuremath{\xi} \ensuremath{\sim} 2.9 \AA{} at 50 K, which is close to 2.99 \AA{}, the shortest distance between the Ru${}^{5+}$ cations along the zig-zag chain.}, number={17}, journal={PHYSICAL REVIEW B}, author={Manuel, P. and Adroja, D. T. and Lindgard, Per-Anker and Hillier, A. D. and Battle, P. D. and Son, Won-Joon and Whangbo, Myung-Hwan}, year={2011}, month={Nov} }
 @article{kan_wu_lee_kang_whangbo_2011, title={On the High Magnetic-Ordering Temperature of the 5d Magnetic Oxide Ca3LiOsO6 Crystallizing in a Trigonal Crystal Structure: Density Functional Analysis}, volume={50}, ISSN={["0020-1669"]}, DOI={10.1021/ic200305a}, abstractNote={The 5d magnetic oxide Ca3LiOsO6 has a trigonal arrangement of its LiOsO6 chains parallel to the c-direction and hence has triangular arrangements of high-spin Os5+ (d3) ions but exhibits no spin frustration and undergoes a long-range antiferromagnetic ordering at a high temperature. The origin of this apparently puzzling observation was examined by evaluating the nearest-neighbor Os−O···O−Os spin exchange interactions of Ca3LiOsO6 on the basis of density functional calculations. Our study shows that, of the two nearest-neighbor interchain spin exchanges, one dominates over the other and that the intrachain spin exchange and the dominating interchain spin exchange are strong and form a three-dimensional antiferromagnetic spin lattice with no spin frustration, which is responsible for the long-range antiferromagnetic ordering of Ca3LiOsO6 at high temperature. In determining the strengths of the Os−O···O−Os exchange interactions of Ca3LiOsO6, the Li+ and Ca2+ ions of the O···Li+···O and O···Ca2+···O linkages are found to play only a minor role.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Kan, Erjun and Wu, Fang and Lee, Changhoon and Kang, Jinhee and Whangbo, Myung-Hwan}, year={2011}, month={May}, pages={4182–4186} }
 @article{tian_wibowo_loye_whangbo_2011, title={On the Magnetic Insulating States, Spin Frustration, and Dominant Spin Exchange of the Ordered Double-Perovskites Sr2CuOsO6 and Sr2NiOsO6: Density Functional Analysis}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic200167j}, abstractNote={The ordered double-perovskites Sr2MOsO6 (M = Cu, Ni) consisting of 3d and 5d transition-metal magnetic ions (M2+ and Os6+, respectively) are magnetic insulators; the magnetic susceptibilities of Sr2CuOsO6 and Sr2NiOsO6 obey the Curie−Weiss law with dominant antiferromagnetic and ferromagnetic interactions, respectively, and the zero-field-cooled and field-cooled susceptibility curves of both compounds diverge below ∼20 K. In contrast, the available density functional studies predicted both Sr2CuOsO6 and Sr2NiOsO6 to be metals. We resolved this discrepancy on the basis of systematic density functional calculations. The magnetic insulating states of Sr2MOsO6 are found only when a substantially large on-site repulsion is employed for the Os atom, although it is a 5d element. The cause for the divergence between the zero-field-cooled and field-cooled susceptibility curves in both compounds and the reason for the difference in their dominant magnetic interactions were investigated by examining their spin exchange interactions.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Wibowo, Arief C. and Loye, Hans-Conrad Zur and Whangbo, Myung-Hwan}, year={2011}, month={May}, pages={4142–4148} }
 @article{koo_lee_whangbo_mcintyre_kremer_2011, title={On the Nature of the Spin Frustration in the CuO2 Ribbon Chains of LiCuVO4: Crystal Structure Determination at 1.6 K, Magnetic Susceptibility Analysis, and Density Functional Evaluation of the Spin Exchange Constants}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic102518t}, abstractNote={The spin-1/2 Cu(2+) ions of LiCuVO(4) form one-dimensional chains along the b direction, and the spin frustration in LiCuVO(4) is described in terms of the nearest-neighbor ferromagnetic exchange J(1) and the next-nearest-neighbor antiferromagnetic exchange J(2) in these chains. Recently, it has become controversial whether or not J(1) is stronger in magnitude than J(2). To resolve this controversy, we determined the crystal structure of LiCuVO(4) at 1.6 K by neutron diffraction, analyzed the magnetic susceptibility of LiCuVO(4) to deduce the Curie-Weiss temperature θ and the J(2)/J(1) ratio, and finally extracted the spin exchange constants of LiCuVO(4) on the basis of density functional calculations. Our work shows unambiguously that the Curie-Weiss temperature θ of LiCuVO(4) is negative in the range of -20 K, so that J(2) is substantially stronger in magnitude than J(1).}, number={8}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Lee, Changhoon and Whangbo, Myung-Hwan and McIntyre, Garry J. and Kremer, Reinhard K.}, year={2011}, month={Apr}, pages={3582–3588} }
 @article{xiang_kan_wei_whangbo_gong_2011, title={Predicting the spin-lattice order of frustrated systems from first principles}, volume={84}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.84.224429}, abstractNote={A novel general method of describing the spin-lattice interactions in magnetic solids was proposed in terms of first principles calculations. The spin exchange and Dzyaloshinskii-Moriya interactions as well as their derivatives with respect to atomic displacements can be evaluated efficiently on the basis of density functional calculations for four ordered spin states. By taking into consideration the spin-spin interactions, the phonons, and the coupling between them, we show that the ground state structure of a representative spin-frustrated spinel, MgCr2 O4, is tetragonally distorted, in agreement with experiments. However, our calculations find the lowest energy for the collinear spin ground state, in contrast to previously suggested non-collinear models.}, number={22}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Kan, E. J. and Wei, Su-Huai and Whangbo, M. -H. and Gong, X. G.}, year={2011}, month={Dec} }
 @article{musfeldt_liu_li_kang_lee_jena_manson_schlueter_carr_whangbo_2011, title={Pressure-Induced Local Structure Distortions in Cu(pyz)F-2(H2O)(2)}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic2008039}, abstractNote={We employed infrared spectroscopy along with complementary lattice dynamics and spin density calculations to investigate pressure-driven local structure distortions in the copper coordination polymer Cu(pyz)F2(H2O)2. Here, pyz is pyrazine. Our study reveals rich and fully reversible local lattice distortions that buckle the pyrazine ring, disrupt the bc-plane O–H···F hydrogen-bonding network, and reinforce magnetic property switching. The resiliency of the soft organic ring is a major factor in the stability of this material. Interestingly, the collective character of the lattice vibrations masks direct information on the Cu–N and Cu–O linkages through the series of pressure-induced Jahn–Teller axis switching transitions, although Cu–F bond softening is clearly identified above 3 GPa. These findings illustrate the importance of combined bulk and local probe techniques for microscopic structure determination in complex materials.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Musfeldt, J. L. and Liu, Z. and Li, S. and Kang, J. and Lee, C. and Jena, P. and Manson, J. L. and Schlueter, J. A. and Carr, G. L. and Whangbo, M. -H.}, year={2011}, month={Jul}, pages={6347–6352} }
 @article{law_reuvekamp_glaum_lee_kang_whangbo_kremer_2011, title={Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4}, volume={84}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.84.014426}, abstractNote={The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO$_4$, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, EPR and dielectric capacitance measurements and density functional evaluations of the intra- and interchain spin exchange interactions. We found type-II multiferroicity below the N\'{e}el temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor ($J_{\rm nn}$) and next-nearest-neighbor ($J_{\rm nnn}$) intra-chain spin exchange interactions. Experimental and theoretical results indicate that the ratio $J_{\rm nn}/J_{\rm nnn}$ is close to 2, putting CuCrO$_4$ in the vicinity of the Majumdar-Ghosh point.}, number={1}, journal={PHYSICAL REVIEW B}, author={Law, J. M. and Reuvekamp, P. and Glaum, R. and Lee, C. and Kang, J. and Whangbo, M. -H. and Kremer, R. K.}, year={2011}, month={Jul} }
 @article{xiang_kan_whangbo_lee_wei_gong_2011, title={Single-ion anisotropy, Dzyaloshinskii-Moriya interaction, and negative magnetoresistance the spin-1/2 pyrochlore R2V2O7}, volume={83}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.83.174402}, abstractNote={The electronic and magnetic properties of spin-1/2 pyrochlores R2V2O7 were investigated on the basis of density-functional calculations. Contrary to the common belief, the spin-1/2 V4+ ions are found to have a substantial easy-axis single-ion anisotropy. The |D/J| ratio deduced from the magnon quantum Hall effect of Lu2V2O7, where J is the nearest-neighbor spin exchange and D is the Dzyaloshinskii-Moriya parameter, is much greater than the value estimated from our calculations (i.e., 0.32 vs. 0.05). We show that this discrepancy is due to the neglect of the single-ion anisotropy of the V4+ ions, and the negative magnetoresistance observed for R2V2O7 arises from a new mechanism.}, number={17}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Kan, E. J. and Whangbo, M. -H. and Lee, C. and Wei, Su-Huai and Gong, X. G.}, year={2011}, month={May} }
 @article{law_hoch_glaum_heinmaa_stern_kang_lee_whangbo_kremer_2011, title={Spin-Peierls transition in the S=1/2 compound TiPO4 featuring large intrachain coupling}, volume={83}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.83.180414}, abstractNote={We investigated the magnetic and structural properties of the quasi-one-dimensional 3${d}^{1}$ quantum chain system TiPO${}_{4}$ ($J~$ 965 K) by magnetic susceptibility, heat capacity, electron spin resonance, x-ray diffraction, and nuclear magnetic resonance (NMR) measurements, and by density functional theory (DFT) calculations. TiPO${}_{4}$ undergoes two magnetostructural phase transitions, one at 111 K and the other at 74 K. Below 74 K, NMR detects two different $^{31}\mathrm{P}$ signals and the magnetic susceptibility vanishes, while DFT calculations evidence a bond alternation of the Ti-Ti distances within each chain. Thus, the 74 K phase transition is a spin-Peierls transition which evolves from an incommensurate phase existing between 111 and 74 K.}, number={18}, journal={PHYSICAL REVIEW B}, author={Law, J. M. and Hoch, C. and Glaum, R. and Heinmaa, I. and Stern, R. and Kang, J. and Lee, C. and Whangbo, M. -H. and Kremer, R. K.}, year={2011}, month={May} }
 @article{manson_lapidus_stephens_peterson_carreiro_southerland_lancaster_blundell_steele_goddard_et al._2011, title={Structural, Electronic, and Magnetic Properties of Quasi-1D Quantum Magnets [Ni(HF2)(pyz)(2)]X (pyz = pyrazine; X = PF6-, SbF6-) Exhibiting Ni-FHF-Ni and Ni-pyz-Ni Spin Interactions}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic102532h}, abstractNote={[Ni(HF(2))(pyz)(2)]X {pyz = pyrazine; X = PF(6)(-) (1), SbF(6)(-) (2)} were structurally characterized by synchrotron X-ray powder diffraction and found to possess axially compressed NiN(4)F(2) octahedra. At 298 K, 1 is monoclinic (C2/c) with unit cell parameters, a = 9.9481(3), b = 9.9421(3), c = 12.5953(4) Å, and β = 81.610(3)° while 2 is tetragonal (P4/nmm) with a = b = 9.9359(3) and c = 6.4471(2) Å and is isomorphic with the Cu-analogue. Infinite one-dimensional (1D) Ni-FHF-Ni chains propagate along the c-axis which are linked via μ-pyz bridges in the ab-plane to afford three-dimensional polymeric frameworks with PF(6)(-) and SbF(6)(-) counterions occupying the interior sites. A major difference between 1 and 2 is that the Ni-F-H bonds are bent (∼157°) in 1 but are linear in 2. Ligand field calculations (LFT) based on an angular overlap model (AOM), with comparison to the electronic absorption spectra, indicate greater π-donation of the HF(2)(-) ligand in 1 owing to the bent Ni-F-H bonds. Magnetic susceptibility data for 1 and 2 exhibit broad maxima at 7.4 and 15 K, respectively, and λ-like peaks in dχT/dT at 6.2 and 12.2 K that are ascribed to transitions to long-range antiferromagnetic order (T(N)). Muon-spin relaxation and specific heat studies confirm these T(N)'s. A comparative analysis of χ vs T to various 1D Heisenberg/Ising models suggests moderate antiferromagnetic interactions, with the primary interaction strength determined to be 3.05/3.42 K (1) and 5.65/6.37 K (2). However, high critical fields of 19 and 37.4 T obtained from low temperature pulsed-field magnetization data indicate that a single exchange constant (J(1D)) alone is insufficient to explain the data and that residual terms in the spin Hamiltonian, which could include interchain magnetic couplings (J(⊥)), as mediated by Ni-pyz-Ni, and single-ion anisotropy (D), must be considered. While it is difficult to draw absolute conclusions regarding the magnitude (and sign) of J(⊥) and D based solely on powder data, further support offered by related Ni(II)-pyz compounds and our LFT and density-functional theory (DFT) results lead us to a consistent quasi-1D magnetic description for 1 and 2.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Manson, Jamie L. and Lapidus, Saul H. and Stephens, Peter W. and Peterson, Peter K. and Carreiro, Kimberly E. and Southerland, Heather I. and Lancaster, Tom and Blundell, Stephen J. and Steele, Andrew J. and Goddard, Paul A. and et al.}, year={2011}, month={Jul}, pages={5990–6009} }
 @article{tang_li_mallik_zhang_clerac_yee_whangbo_mungalimane_holmes_2011, title={Synthesis and Characterization of Di- and Trivalent Pyrazolylborate beta-Diketonates and Cyanometalates}, volume={50}, ISSN={["1520-510X"]}, DOI={10.1021/ic200464t}, abstractNote={The syntheses, structures, and magnetic properties of a series of di- and trivalent hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) cyanomanganates are described. Treatment of tris(acetylacetonate)manganese(III) [Mn(acac)(3)] with KTp* and tetra(ethyl)ammonium cyanide affords [NEt(4)][(Tp*)Mn(II)(κ(2)-acac)(CN)] (1), as the first monocyanomanganate(II) complex; attempted oxidation of 1 with iodine affords {(Tp*)Mn(II)(κ(2)-acac(3-CN))}(n) (2) as a one-dimensional chain and bimetallic {[NEt(4)][(Tp*)Mn(II)(κ(2)-acac(3-CN))](2)(μ-CN) (3) as the major and minor products, respectively. A fourth complex, [NEt(4)][(Tp*)Mn(II)(η(2)-acac(3-CN))(η(1)-NC-acac)] (4), is obtained via treatment of Mn(acac(3-CN))(3) with KTp* and [NEt(4)]CN, while [NEt(4)](2)[Mn(II)(CN)(4)] (5) was prepared from manganese(II) trifluoromethanesulfonate and excess [NEt(4)]CN. Tricyanomanganate(III) complexes, [cat][(Tp*)Mn(III)(CN)(3)] [cat = NEt(4)(+), 7; PPN(+), 8], are prepared via sequential treatment of Mn(acac(3-CN))(3) with KTp*, followed by [NEt(4)]CN, or [cat](3)[Mn(III)(CN)(6)] with (Tp*)SnBu(2)Cl. Magnetic measurements indicate that 1, 2, and 4 contain isotropic Mn(II) (S = (5)/(2); g = 2.00) centers, and no long-range magnetic ordering is found above 1.8 K. Compounds 7 and 8 contain S = 1 Mn(III) centers that adopt singly degenerate spin ground states without orbital contributions to their magnetic moments.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Tang, Minao and Li, Dongfeng and Mallik, Uma Prasad and Zhang, Yuan-Zhu and Clerac, Rodolphe and Yee, Gordon T. and Whangbo, Myung-Hwan and Mungalimane, Amshumali and Holmes, Stephen M.}, year={2011}, month={Jun}, pages={5153–5164} }
 @article{zheng_huang_wei_dai_whangbo_2011, title={Synthesis and optical properties of amorphous C-Si-O particles}, volume={131}, ISSN={["1872-7883"]}, DOI={10.1016/j.jlumin.2010.10.001}, abstractNote={Amorphous C–Si–O particles, prepared by pyrolyzing PDMS in a horizontal furnace using the carrier gas N2/H2 at 900 °C, were characterized by electron microscopy, X-ray diffraction, FTIR spectroscopy, X-ray photoelectron spectroscopy and fluorescence spectroscopy. The particles possess four luminescence peaks at 440, 465, 533 and 620 nm, and produce stable red, green or blue light emissions at room temperature when irradiated with appropriate wavelengths, the four peaks attribute to different defect centers in the particles. And the particles exhibit the highest photoluminescence intensity when annealed at 600 °C.}, number={2}, journal={JOURNAL OF LUMINESCENCE}, author={Zheng, Liren and Huang, Baibiao and Wei, Jiyong and Dai, Ying and Whangbo, Myung-Hwan}, year={2011}, month={Feb}, pages={218–224} }
 @article{manson_warter_schlueter_lancaster_steele_blundell_pratt_singleton_mcdonald_lee_et al._2011, title={[Cu(HF2)(2)(pyrazine)](n): A Rectangular Antiferromagnetic Lattice with a Spin Exchange Path Made Up of Two Different FHF- Bridges}, volume={50}, ISSN={["1521-3773"]}, DOI={10.1002/anie.201006653}, abstractNote={The two-dimensional antiferromagnet [Cu(HF2)2(pyz)]n (pyz=pyrazine) has a rectangular lattice (see picture) displaying two types of FHF− bridging modes. The spin exchange through Cu-(FHF)2-Cu is about 90 % stronger than through Cu-pyz-Cu, and the μ1,1-coordinated FHF−, which is close in nature to F−⋅⋅⋅HF, is largely responsible for the exchange. C black, Cu red, F green, H cyan.}, number={7}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Manson, Jamie L. and Warter, Michelle L. and Schlueter, John A. and Lancaster, Tom and Steele, Andrew J. and Blundell, Stephen J. and Pratt, Francis L. and Singleton, John and McDonald, Ross D. and Lee, Changhoon and et al.}, year={2011}, pages={1573–1576} }
 @article{liu_huang_wang_qin_zhang_wei_dai_wang_whangbo_2010, title={Amino acid-assisted synthesis of ZnO twin-prisms and functional group's influence on their morphologies}, volume={507}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2010.07.192}, abstractNote={ZnO twin-prisms were prepared by a simple solvothermal process with glutamic acid as surface modification agent in ethanol. Compared with the twin-cones that were obtained when glutamic acid was absent, the ZnO twin-prisms have optimized crystallinity with high symmetry, sharp crystal edges and few defects. Probable reaction mechanism between ZnO and glutamic acid was proposed based on our experimental analysis. Then it was verified by a series of comparison experiments by employing glycine, acetic acid and ethylamine as surface modification agents. Our results indicate that both alkaline and acidic groups play an important role on the formation of ZnO twin-prisms, and when either of them was absent, twin-prism structures cannot be obtained. The photoluminescence properties of as-prepared ZnO twin-prisms and twin-cones were also studied.}, number={1}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Liu, Haixia and Huang, Baibiao and Wang, Zeyan and Qin, Xiaoyan and Zhang, Xiaoyang and Wei, Jiyong and Dai, Ying and Wang, Peng and Whangbo, Myung-Hwan}, year={2010}, month={Sep}, pages={326–330} }
 @article{lee_whangbo_koehler_2010, title={Analysis of Electronic Structures and Chemical Bonding of Metal-rich Compounds. 2. Presence of Dimer (T-T)(4-) and Isolated T2- Anions in the Polar Intermetallic Cr5B3-Type Compounds AE(5)T(3) (AE = Ca, Sr; T = Au, Ag, Hg, Cd, Zn)}, volume={636}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.200900421}, abstractNote={Abstract First principles density functional calculations were carried out to probe the oxidation states of the transition‐metal and alkaline‐earth elements in the Cr 5 B 3 ‐type compounds AE 5 T 3 consisting of T 2 dimers and isolated T atoms (i.e., Ca 5 Au 3 , Ca 5 Ag 3 , Ca 5 Hg 3 , Sr 5 Cd 3 , and Ca 5 Zn 3 ). The electronic structures of all these AE 5 T 3 compounds are best described as [( AE 2+ ) 5 ( T – T ) 4– ( T 2– )]+4e – . In the covalent bonding of the AE 2+ ions with the transition metal anions T 2– , the ( n –1)d orbitals of AE 2+ contribute more than the n s and n p orbitals of AE 2+ .}, number={1}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Lee, Changhoon and Whangbo, Myung-Hwan and Koehler, Juergen}, year={2010}, pages={36–40} }
 @article{tian_lee_kan_wu_whangbo_2010, title={Analysis of the Magnetic Structure and Ferroelectric Polarization of Monoclinic MnSb2S4 by Density Functional Theory Calculations}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101351b}, abstractNote={Monoclinic MnSb2S4 consists of MnS4 chains made up of edge-sharing MnS6 octahedra and adopts a (0, 0.369, 0) magnetic superstructure below 25 K. This ordered magnetic structure, in which the spins of each MnS4 chain possess a helical spin arrangement, has C2′ symmetry. On the basis of density functional theory calculations, we explored the origin of the observed noncollinear spin arrangement of MnSb2S4 by evaluating its spin exchanges to find that spin exchanges are frustrated not only within each MnS4 chain but also between adjacent MnS4 chains. Our analysis predicts that MnSb2S4 is a multiferroic with a ferroelectric polarization of ∼14 μC/m2 along the chain direction, and a field-induced reversal of the ferroelectric polarization of MnSb2S4 can occur by reversing the direction of the helical spin rotation in each MnS4 chain.}, number={23}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Lee, Changhoon and Kan, Erjun and Wu, Fang and Whangbo, Myung-Hwan}, year={2010}, month={Dec}, pages={10956–10959} }
 @article{mentre_kabbour_ehora_tricot_daviero-minaud_whangbo_2010, title={Anion-Vacancy-Induced Magneto-Crystalline Anisotropy in Fluorine-Doped Hexagonal Cobaltites}, volume={132}, ISSN={["1520-5126"]}, DOI={10.1021/ja100170m}, abstractNote={The two cobalt hexagonal perovskites 6H-Ba(6)Co(6)F(0.93)O(16) and 10H-Ba(5)Co(5)F(0.77)O(12.88) were prepared, and their structures were examined by X-ray and neutron diffraction and by (19)F solid state NMR spectroscopy. The magnetic and transport properties of these compounds were probed by magnetic susceptibility and electrical resistivity measurements, and their electronic structures by density functional and tight-binding calculations. The [BaOF(1-x)] layers of these compounds create corner-sharing tetrahedral Co(2)O(7) dimers at the interface between their face-sharing octahedral oligomers. Our density functional calculations leads to an unambiguous charge distribution model, which assigns high-spin Co(3+) ions for the tetrahedral sites and low-spin Co(3+)/Co(4+) ions for the octahedral sites, and this model should be valid for the parent BaCoO(3-delta) and the related oxychlorides and oxybromides as well. The F(-) vacancies in the [BaOF(1-x)] layers cause a strong distortion in the tetrahedral dimer Co(2)O(7), which in turn affects the spin orientation of the high-spin Co(3+) ions of the CoO(4) tetrahedra, i.e., parallel to the c-direction in Ba(6)Co(6)F(1-x)O(16-delta) but perpendicular to the c-direction in Ba(5)Co(5)F(1-x)O(13-delta). This difference in the spin orientations is related to the d-states of the distorted CoO(4) tetrahedra with high-spin Co(3+) (d(6)) ion on the basis of tight binding calculations and spin-orbit coupling as perturbation.}, number={13}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Mentre, Olivier and Kabbour, Houria and Ehora, Ghislaine and Tricot, Gregory and Daviero-Minaud, Sylvie and Whangbo, Myung-Hwan}, year={2010}, month={Apr}, pages={4865–4875} }
 @article{tong_lee_whangbo_kremer_simon_koehler_2010, title={Cooperative Jahn-Teller distortion leading to the spin-1/2 uniform antiferromagnetic chains in triclinic perovskites AgCuF3 and NaCuF3}, volume={12}, ISSN={["1293-2558"]}, DOI={10.1016/j.solidstatesciences.2009.02.028}, abstractNote={Abstract Polycrystalline samples of AgCuF 3 , isostructural with NaCuF 3 , were synthesized by solid state reaction and characterized by powder X-ray diffraction. The magnetic properties of AgCuF 3 and NaCuF 3 were examined by measuring their magnetic susceptibilities and evaluating their spin exchange interactions. The three-dimensional CuF 3 network of corner-sharing CuF 6 octahedra present in AgCuF 3 and NaCuF 3 shows a cooperative Jahn–Teller distortion such that their magnetic susceptibilities above 50 K are well described by an S  = 1/2 Heisenberg uniform antiferromagnetic chain model with average spin exchange of J / k B  ≈ −300 and −180 K, respectively. The relative strengths of these interactions are well reproduced by spin dimer analysis based on tight-binding calculations, but not by mapping analysis based on first principles density functional calculations.}, number={5}, journal={SOLID STATE SCIENCES}, author={Tong, J. and Lee, C. and Whangbo, M. -H. and Kremer, R. K. and Simon, A. and Koehler, J.}, year={2010}, month={May}, pages={680–684} }
 @article{law_hoch_whangbo_kremer_2010, title={Description of Anhydrous (Black) Dioptase as a S=1/2 Uniform Antiferromagnetic Chain System}, volume={636}, ISSN={["0044-2313"]}, DOI={10.1002/zaac.200900403}, abstractNote={Abstract The structural and magnetic properties of anhydrous (black) dioptase, CuSiO 3 , were investigated by carrying out single‐crystal X‐ray diffraction, specific heat, and magnetic susceptibility measurements as well as by performing spin dimer analysis based on extended Hückel tight‐binding calculations. Our spin dimer analysis indicates that black dioptase is a S = 1/2 uniform antiferromagnetic chain system with the interchain spin exchange weaker than the intrachain exchange by three orders of magnitude. Specific heat and magnetic susceptibility measurements show that the intrachain exchange is –174(2) K, and the interchain exchange is of the order of ~2 K. They lead to long‐range magnetic ordering at about 5 K as evidenced by a broad anomaly in the specific heat.}, number={1}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Law, Joseph M. and Hoch, Constantin and Whangbo, Myung-Hwan and Kremer, Reinhard K.}, year={2010}, pages={54–61} }
 @article{schlueter_wiehl_park_souza_lang_koo_whangbo_2010, title={Enhanced Critical Temperature in a Dual-Layered Molecular Superconductor}, volume={132}, ISSN={["1520-5126"]}, DOI={10.1021/ja105854m}, abstractNote={Single-crystal X-ray diffraction has shown that the high-critical-temperature (Tc) phase of the filamentary molecular superconductor (BEDT-TTF)2Ag(CF3)4(1,1,2-trichloroethane) [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] contains layers of BEDT-TTF radical cations with alternating κ- and α′-type packing motifs. This molecule-based superconductor with dual BEDT-TTF packing motifs has a Tc five times higher than that of its polymorph that contains only κ-type packing.}, number={46}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Schlueter, John A. and Wiehl, Leonore and Park, Hyunsoo and Souza, Mariano and Lang, Michael and Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2010}, month={Nov}, pages={16308–16310} }
 @article{kan_xiang_wu_lee_yang_whangbo_2010, title={Ferrimagnetism in zigzag graphene nanoribbons induced by main-group adatoms}, volume={96}, number={10}, journal={Applied Physics Letters}, author={Kan, E. and Xiang, H. J. and Wu, F. and Lee, C. and Yang, J. L. and Whangbo, M. H.}, year={2010} }
 @article{kan_xiang_lee_wu_yang_whangbo_2010, title={Ferroelectricity in Perovskites with s(0) A-Site Cations: Toward Near-Room-Temperature Multiferroics}, volume={49}, ISSN={["1433-7851"]}, DOI={10.1002/anie.200905997}, abstractNote={The origin of the ferroelectricity in the indium-based multiferroic perovskites (In1−xMx)MO3 (M=Mn0.5Fe0.5), and the question of how to lower their magnetic ordering (TN) and the ferroelectric Curie temperatures, was investigated by density functional calculations. The analyses explain why TN is near room temperature and why the perovskites with s0 and s2 A-site cations have similar ferroelectric distortions. Magnetic ferroelectric (FE) materials (that is, multiferroics) have received much attention and can have wide technological applications owing to the possibility of controlling their electric properties and their magnetic properties by electric fields.1, 2 An important class of multiferroic and FE3 materials is based on perovskites, ABO3, with two different cations A and B (for example A2+ and B4+ or A3+ and B3+), in which corner-sharing BO6 octahedra form the three-dimensional lattice with every B8 cube containing one A cation. An ideal cubic perovskite, in which the B-OB bonds are linear with A located at the center of each B8 cube (thus forming a AO12 polyhedron), is expected when the tolerance factor τ=(rO+rA)/(rO+rB) is unity (rA and rB are the ionic radii of the A and B cations, respectively, with rO as that of the O2− anion). In most cases, the A cations are small, so that τ<1 and the AO bonds are too long to maintain the ideal cubic structure. Consequently, the A cation moves away from the center of the B8 cube, which is accompanied by the bending of the B-O-B bonds and the rotation of the BO6 octahedra to form a lower-coordinate AOn polyhedron (n<12) with short AO bonds. The distortion of the ideal cubic perovskite toward a non-centrosymmetric FE structure requires another local instability apart from τ<1, namely, the second-order Jahn–Teller (SOJT) instability4–6 of the A-site and/or B-site cation. As found for PbTiO3,7 PbVO3,8 and BiCoO3,9 moving the A cation toward the center of one B4 face (Figure 1 a) leads to a tetragonal FE structure with space group P4mm. The B cations move away from the approaching A cations such that the coordinate environment of each B cation is more like a BO5 square pyramid with shortened axial BO bond. In PbTiO3, PbVO3, and BiCoO3, the s2 A-site cations Pb2+ and Bi3+ are susceptible to a SOJT distortion, which mixes the empty 6p orbital of A into the filled 6s2 orbital of A hence forming a lone pair on A.4 In PbTiO3, the B-site cation Ti4+ (d0) is also susceptible to a SOJT distortion, which mixes the empty Ti 3d orbitals into the filled 2p orbitals of the oxygen atom of the axial TiO bond.5, 6 Thus, in PbTiO3, the need to make short PbO bonds and the SOJT instabilities of both Pb2+ and Ti4+ ions cooperate to give rise to the observed FE distortion.10, 11 Perspective views of the local structures around the A cation in three perovskites ABO3, where the large, medium, and small circles refer to the A, B, and O atoms, respectively. a) The FE distortion in ABO3 with space group P4mm. Only eight corner-sharing BO5 square pyramids and one A cation are shown. b) The FE distortion of ABO3 with space group R3c. For simplicity, only the two BO6 octahedra at the two corners of the B8 cube along the body-diagonal direction and the AO3 unit lying between the two octahedra are shown. The AO3 unit merges with the upper BO6 octahedron to form a distorted AO6 octahedron, which shares its face with the upper BO6 octahedron, resulting in the face-sharing octahedral dimer ABO9. c) The PE structure of ABO3 with space group Rc, by which one FE structure is converted into the other FE structure with opposite polarization. The B cation in each BO6 octahedron is located at the center of the O6 octahedron, and the AO3 unit lying at the midpoint between the two octahedra is planar. Another type of the A-cation displacement from the center of the B8 cube is the movement toward one corner of the B8 cube along the body-diagonal direction (that is, the C3 rotational axis; Figure 1 b) to form a non-centrosymmetric FE trigonal structure with space group R3c, as found for BiFeO3.12 The movement of the A cation toward one corner is equivalent to that toward the opposite corner, and the two energetically-equivalent FE structures are mutually interconverted through the centrosymmetric paraelectric (PE) trigonal structure with space group Rc (Figure 1 c).13, 14 For BiFeO3, the FE Curie temperature (TE=1123 K)15 and the three-dimensional antiferromagnetic ordering temperature (TN=650 K)16 are well above room temperature. For practical applications, it is highly desirable to find multiferroics with both TE and TN close to room temperature. Recently, Belik et al.17 have achieved a partial success toward this goal; they synthesized the indium-based multiferroics (In1−xMx)MO3 (x≈0.112-0.176; M=Mn0.5Fe0.5) that have a TN value close to room temperature; however, TE is still high (for x=0.176, TN≈270 K and TE is expected to be above 670 K, but the phase is transformed irreversibly to a corundum-type structure above 670 K). These multiferroics, which are isostructural with BiFeO3, are quite surprising in two aspects. First, magnetic ordering of a system made up of magnetic ions is generally prevented when disorder is present in the system. However, long-range magnetic ordering occurs near room temperature despite the expected disorder in the A and B sites (that is, the statistical distribution of high-spin Mn3+ and Fe3+ cations). Second, it is believed that the strong FE distortion in perovskites with s2 A-site cations, such as BiFeO3, PbTiO3, PbVO3, and BiCoO3, arises from the need to create space for the lone pair on A. However, a strong FE distortion that is almost as strong as found for BiFeO3 occurs in the indium-based multiferroics, although the A-site cations (In3+, Mn3+, and Fe3+) do not possess a lone pair. Herein, we explore these puzzling observations on the basis of systematic density functional calculations for BiFeO3 and model perovskites ABO3 (A=Ga, In, Tl; B=Mn, Fe, Mn0.5Fe0.5) that simulate the indium-based multiferroics (In1−xMx)MO3. Unless stated otherwise, our calculations were carried out for the antiferromagnetic (AFM) states of ABO3 (A=Ga, In, Tl; B=Mn, Fe, Mn0.5Fe0.5) and BiFeO3 in which all nearest-neighbor (NN) spins of the B-site cations are antiferromagnetically coupled. In the hexagonal setting of the trigonal space group R3c, a unit cell of these compounds has six layers of B cations perpendicular to the c axis. To simulate the random arrangement of the Mn3+ and Fe3+ ions in A(Mn0.5Fe0.5)O3, we adopted the ordered arrangement in which layers of Mn3+ ions alternate with layers of Fe3+ ions along the c direction. This arrangement is statistically most probable because each B8 cube is given by Mn4Fe4 such that all NN cations are different. In our GGA+U calculations for the FE structures of ABO3 (A=Ga, In, Tl; B=Mn, Fe, Mn0.5Fe0.5) and BiFeO3 (with space group R3c), the positions of the atoms were fully optimized but the cell parameters were kept constant at the experimental values. The cell parameters of ABO3 (A=Ga, In, Tl; B=Mn, Fe, Mn0.5Fe0.5) were fixed at those found for (In1−xMx)MO3 (x≈0.176; M=Mn0.5Fe0.5).17 The results of our structure optimizations for the FE structures of ABO3 are summarized in terms of the three parameters ΔrA, ΔzA and ΔzB (Figure 1 b), where ΔrA is the A-cation displacement from the center of the B8 cube to the actual position of A in the B8 cube; the strength of the AO6 (BO6) octahedron distortion is measured by the displacement ΔzA (ΔzB) from the center of the O6 octahedron to the actual position of the A (B) cation. Given that the z axis taken along the c direction of the hexagonal setting (i.e., the body-diagonal direction of the B8 cube; Figure 1 b) shows that ΔzA<0 and ΔzB>0. The values of ΔrA are summarized in Table 1, and the ΔzA and ΔzB values are given in Table 2. The ΔrA values are substantial, and are largely determined by the A cation. For a given ABO3 series and BiFeO3, the ΔrA values decrease in the order Ga3+>In3+>Tl3+>Bi3+, which reflects that the A-cation size increases in the order Ga3+<In3+<Tl3+<Bi3+. Table 2 reveals that the ΔzA and ΔzB values are substantial and are largely determined by the A cation; the |ΔzA| values increase in the order Ga3+<In3+<Tl3+, and the ΔzB values decrease with increasing |ΔzA|. The ΔzA and ΔzB values of BiFeO3 are close to those of TlFeO3. A A(Mn0.5Fe0.5)O3 AMnO3 AFeO3 Ga 0.588 0.550 0.593 In 0.504 0.479 0.559 Tl 0.321 0.309 0.339 B Parameter GaBO3 InBO3 TlBO3 Mn0.5Fe0.5 ΔzB(Mn) 0.235 0.185 0.108 ΔrA(Mn) −0.360 −0.479 −0.747 ΔzB(Fe) 0.282 0.234 0.137 ΔrA(Fe) −0.318 −0.449 −0.720 Mn ΔzB 0.226 0.182 0.136 ΔrA −0.345 −0.467 −0.745 Fe ΔzB 0.269 0.216 0.122 ΔrA −0.344 −0.468 −0.732 As described above, the FE distortion of the indium-based multiferroics (In1−xMx)MO3 (x≈0.112–0.176; M=Mn0.5Fe0.5) is very similar in nature and magnitude to that found in BiFeO3, which suggests that the origin of their FE distortions is identical. The face-sharing octahedral dimer ABO9 (Figure 1 b) along the body-diagonal direction of the B8 cube can be regarded as a result of the interaction between the BO6 octahedron and the AO3 pyramid (Figure 2 a). As depicted in Figure 2 b, the AO3 pyramid has two hydrid orbitals ϕ+ and ϕ− made up of the ns and np orbitals (n=4, 5, 6 for Ga3+, In3+, and Tl3+, respectively).4 In the case of the s2 cation Bi3+, the ϕ+ orbital is doubly occupied to become a lone pair, whilst the ϕ− orbital is empty. In the case of the s0 cations Ga3+, In3+ and Tl3+, both ϕ+ and ϕ− orbitals are empty. The energy lowering associated with the interaction of the AO3 pyramid with the BO6 octahedron occurs primarily from the interaction of the empty ϕ− orbital with the filled 2p orbitals of the three oxygen atoms that form the AO bonds. This interaction is the driving force for the SOJT distortion of the A-site cations, and is therefore independent of whether the A-site cation is an s0 or an s2 cation. It was shown above that the |ΔzA| values increase in the order Ga3+<In3+<Tl3+, whereas the ΔzB values decrease with increasing |ΔzA|. The extent of the A3+ cation displacement in the AO6 octahedron from the center of the O6 octahedron is related to the extension of the A3+-cation np orbital (n=4, 5, and 6 for Ga3+, In3+, and Tl3+, respectively); the maximum overlap of the A3+ cation ϕ− orbital (hence the np orbital) with the O 2p orbitals of the three oxygen atoms forming the AO bonds should occur at a larger |ΔzA| value as the A cation is varied from Ga3+ to In3+ to Tl3+. The involvement of the In3+ cation 5p orbitals in the FE distortion of the perovskite InBO3 (B=Mn, Fe, Mn0.5Fen0.5) can be seen from the plots of the density of states (DOS) calculated for the FE and PE structures of InFeO3 (Figure 3). The PE structure has more unoccupied In 5p states in a lower energy region than does the FE structure. This result means that more In 5p states are involved in bonding with the O 2p states in the FE state than in the PE state, as expected from the SOJT distortion involving the In3+ cation. Similar interactions should occur between the np orbitals of the A-site cation and the O 2p orbitals in the FE structure of ABO3 with space group P4 mm, as found for PbVO3.18 a) The face-sharing octahedral dimer ABO9 in the FE structure of ABO3 with space group R3c in terms of the BO6 octahedron and the AO3 pyramid. b) The two hybrid orbitals ϕ+ and ϕ− of the AO3 pyramid. Plots of the projected DOS (states/eV per two formula units) calculated for the In 5s and In 5p orbitals in the FE and PE structures of InFeO3. The up- and down-spin densities are indicated by plus and minus DOS values, respectively. We then examined the FE polarization of (In1−xMx)MO3 (x≈0.176; M=Mn0.5Fe0.5) by considering only the perovskites AFeO3 (A=Ga, In, Tl), because the FE distortion is largely determined by the A cation, as discussed above. As found for BiFeO3,13, 14 the most probable PE structure of AFeO3 (A=Ga, In, Tl) has the centrosymmetric structure with space group Rc.19 The rhombohedral setting of this structure has the positions Fe(0,0,0), In(1/4,1/4,1/4), and O(x,1/2−x,1/4). Our structure optimizations for the PE structures lead to x=0.6023, 0.6399, 0.6405, and 0.6707 for GaFeO3, InFeO3, TlFeO3, and BiFeO3, respectively. Given the FE and PE structures of AFeO3, we calculated their FE polarizations P (along the body-diagonal direction of the B8 cube) on the basis of the Berry phase method,20 which leads to 46, 74, and 139 μC cm−2 for GaFeO3, InFeO3, and TlFeO3, respectively. These values are comparable to 98.7 μC cm−2 calculated for BiFeO3.13, 14 Experimentally, the FE polarization of (In1−xMx)MO317 is comparable in magnitude to that of BiFeO313, 14 (P≈1 μC cm−2 for x=0.143 versus 2–6 μC cm−2). To understand why (In1−xMx)MO3 (M=Mn0.5Fe0.5) has a significantly lower TN (about 270 K for x≈0.176) than does BiFeO3 (650 K), it is necessary to evaluate the NN spin exchange parameters J of InMO3 (M=Mn, Fe, Mn0.5Fe0.5) and BiFeO3 by calculating the energies of the two ordered spin states for InMO3 and BiFeO3; that is, the AFM state considered so far and the ferromagnetic (FM) state in which all NN spins are ferromagnetically coupled. By mapping the energy difference between the two states onto the corresponding energy difference expected from the spin Hamiltonian expressed in terms of J,21, 22 we obtain J=−18.8, −14.6, +10.4, and −6.1 meV for BiFeO3, InFeO3, InMnO3, and In(Mn0.5Fe0.5)O3, respectively. Namely, the AFM state is more stable than the FM state for InFeO3 and In(Mn0.5Fe0.5)O3, as found for BiFeO3, whereas the opposite is the case for InMnO3.23, 24 Note that the J value of In(Mn0.5Fe0.5)O3 is smaller than those of InFeO3 and BiFeO3 by a factor of about 2.5–3. In the mean field approximation,25 TN scales linearly with |J|, so that the TN of In(Mn0.5Fe0.5)O3 is estimated to be circa 220–260 K from TN=650 K for BiFeO3. The latter value is quite close to that found for the indium-based multiferroics (In1−xMx)MO3 (M=Mn0.5Fe0.5) (i.e., about 270 K for x≈0.176).17 Therefore, the three-dimensional magnetic ordering of (In1−xMx)MO3 (M=Mn0.5Fe0.5) near room temperature arises from two factors: one is that the statistically most probable distribution of the Mn3+ and Fe3+ ions in the b sites leads to the three-dimensional arrangement in which the spin exchange paths between these magnetic ions are largely given by the Mn-O-Fe superexchanges; the other factor is that the Mn-O-Fe superexchange is weaker than the Fe-O-Fe superexchange by a factor of about three. Finally, we addressed the question of how to lower TE of perovskite multiferroics with s0 A-site cations by considering AFeO3 (A=Ga, In, Tl, Bi). It is not surprising that the indium-based multiferroics (In1−xMx)MO3 (M=Mn0.5Fe0.5) have a high TE and a high FE polarization because their FE distortion is nearly as strong as that found for BiFeO3. Qualitatively, TE of AFeO3 (A=Ga, In, Tl, Bi) is expected to be lowered when the stability of the FE structure with respect to the PE structure is reduced. Our calculations for the optimized FE and PE structures of AFeO3 predict that the FE structure is more stable than the PE structure by 0.31, 0.45, 0.20, and 0.32 eV per formula unit for A=Ga, In, Tl, and Bi, respectively, suggesting that the tendency for the A-site cation to undergo an FE distortion should decrease in the order In3+>Bi3+, Ga3+>Tl3+. Therefore, TlFeO3 would have a lower TE value than does BiFeO3. It would be of interest to prepare the thallium analogue of the indium-based multiferroics, such as (Tl1−xMx)MO3 (M=Mn0.5Fe0.5). Another interesting compound would be (Ga1−xMx)MO3 (M=Mn0.5Fe0.5), because the presence of Mn3+ and Fe3+ ions at the A-cation sites would reduce the tendency for the Ga3+ ions to undergo an FE distortion, thus lowering TE . In summary, our work explains why TN of the indium-based multiferroic perovskites (In1−xMx)MO3 (M=Mn0.5Fe0.5) is near room temperature and why the perovskites with s0 and s2 A-site cations have similar ferroelectric distortions. Possible perovskites with TE lower than that of (In1−xMx)MO3 are expected from (Tl1−xMx)MO3 (M=Mn0.5Fe0.5) and (Ga1−xMx)MO3 (M=Mn0.5Fe0.5). The calculations employed the projector-augmented wave method26 encoded in the Vienna ab initio simulation package,27 the PW91 functional form28 of the generalized gradient approximation (GGA), and the plane-wave cut-off energy of 400 eV. The GGA plus on-site repulsion U method29 (GGA+U) was used to properly describe the electron correlation associated with the Mn and Fe 3d states with several values of U for both manganese and iron. Similar results are obtained from the use of other U values, so we report only those from U=4.5 eV.}, number={9}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Kan, Erjun and Xiang, Hongjun and Lee, Changhoon and Wu, Fang and Yang, Jinlong and Whangbo, Myung-Hwan}, year={2010}, pages={1603–1606} }
 @article{tassel_kang_lee_hernandez_qiu_paulus_collet_lake_guidi_whangbo_et al._2010, title={Ferromagnetically Coupled Shastry-Sutherland Quantum Spin Singlets in (CuCl)LaNb2O7}, volume={105}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.105.167205}, abstractNote={Using inelastic neutron scattering, x-ray, neutron diffraction, and the first-principle calculation techniques, we show that the crystal structure of the two-dimensional quantum spin system (CuCl)LaNb$_2$O$_7$ is orthorhombic with $Pbam$ symmetry in which CuCl$_4$O$_2$ octahedra are tilted from their high symmetry positions and the Cu$^{2+} (s = 1/2)$ ions form a distorted square lattice. The dominant magnetic interactions are the fourth nearest neighbor antiferromagnetic interactions with a Cu-Cl--Cl-Cu exchange path, which lead to the formation of spin singlets. The two strongest interactions between the singlets are ferromagnetic, which makes (CuCl)LaNb$_2$O$_7$ the first system of ferromagnetically coupled Shastry-Sutherland quantum spin singlets.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Tassel, C. and Kang, J. and Lee, C. and Hernandez, O. and Qiu, Y. and Paulus, W. and Collet, E. and Lake, B. and Guidi, T. and Whangbo, M-H and et al.}, year={2010}, month={Oct} }
 @article{koo_whangbo_2010, title={Finite Magnetization Plateau from a Two-Dimensional Antiferromagnet: Density Functional Analysis of the Magnetic Structure of Cu-3(P2O6OH)(2)}, volume={49}, ISSN={["0020-1669"]}, DOI={10.1021/ic100906s}, abstractNote={We evaluated the intrachain and interchain spin exchanges of Cu3(P2O6OH) consisting of (Cu2−Cu2−Cu1)∞ chains by density functional calculations to find that the magnetic properties of Cu3(P2O6OH)2 are not governed by the J1−J2−J2 trimer chain along the c-direction, but by a two-dimensional (2D) antiferromagnetic lattice in which J1−J3−J3 trimer chains along the (a−c/2)-direction are interconnected by J6 monomer chains along the a-direction. Despite its 2D character, Cu3(P2O6OH)2 shows a 1/3 magnetization plateau because it is a spin-1/2 trimer system with one dominant antiferromagnetic dimer exchange.}, number={20}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2010}, month={Oct}, pages={9253–9256} }
 @article{tang_li_mallik_withers_brauer_rhodes_clerac_yee_whangbo_holmes_2010, title={First Structurally Characterized Tricyanomanganate(III) and its Magnetic {(Mn2M2II)-M-III} Complexes (M-II = Mn, Ni)}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic1006605}, abstractNote={Treatment of tris(3-cyano-2,4-pentanedionato)manganese(III) with KTp*, followed by [NEt4]CN affords [NEt4][(Tp*)MnIII(CN)3] (1); subsequent treatment of 1 with divalent triflates (OTf) and 2,2′-bipyridine (bpy) affords {MnIII2MII2} complexes (MII = Mn, 2; Ni, 3). Magnetic measurements show that 1−3 exhibit ST = 1, 3, and 4 spin ground states, respectively.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Tang, Minao and Li, Dongfeng and Mallik, Uma Prasad and Withers, Jeffrey R. and Brauer, Shari and Rhodes, Michael R. and Clerac, Rodolphe and Yee, Gordon T. and Whangbo, Myung-Hwan and Holmes, Stephen M.}, year={2010}, month={Jun}, pages={4753–4755} }
 @article{dorolti_cario_corraze_janod_vaju_koo_kan_whangbo_2010, title={Half-Metallic Ferromagnetism and Large Negative Magnetoresistance in the New Lacunar Spinel GaTi3VS8}, volume={132}, ISSN={["0002-7863"]}, DOI={10.1021/ja908128b}, abstractNote={The lacunar spinel compounds GaTi4−xVxS8 (0 < x < 4), consisting of Ti4−xVx tetrahedral clusters, were prepared and their structures were determined by powder X-ray diffraction. The electronic structures of GaTi4−xVxS8 (x = 0, 1, 2, 3) were examined by density functional calculations, and the electrical resistivity and magnetic susceptibility of these compounds were measured. Our calculations predict that GaTi3VS8 is a ferromagnetic half-metal, and this prediction was confirmed by magnetotransport experiments performed on polycrystalline samples of GaTi3VS8. The latter reveal a large negative magnetoresistance (up to 22% at 2 K), which is consistent with the intergrain tunnelling magnetoresistance expected for powder samples of a ferromagnetic half-metal and indicates the presence of high spin polarization greater than 53% in GaTi3VS8.}, number={16}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Dorolti, Eugen and Cario, Laurent and Corraze, Benoit and Janod, Etienne and Vaju, Cristian and Koo, Hyun-Joo and Kan, Erjun and Whangbo, Myung-Hwan}, year={2010}, month={Apr}, pages={5704–5710} }
 @article{tomiyasu_kageyama_lee_whangbo_tsujimoto_yoshimura_taylor_llobet_trouw_kakurai_et al._2010, title={Magnetic excitations in infinite-layer antiferromagnetic insulator}, volume={79}, number={3}, journal={Journal of the Physical Society of Japan}, author={Tomiyasu, K. and Kageyama, H. and Lee, C. and Whangbo, M. H. and Tsujimoto, Y. and Yoshimura, K. and Taylor, J. W. and Llobet, A. and Trouw, F. and Kakurai, K. and et al.}, year={2010} }
 @article{white_lee_gunaydin-sen_tung_christen_wang_turnbull_landee_mcdonald_crooker_et al._2010, title={Magneto-optical properties and charge-spin coupling in the molecular (2,3-dmpyH)(2)CuBr4 spin-ladder material}, volume={81}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.81.052407}, abstractNote={We investigated the magnetic and optical properties of ${(2,3\text{-dmpyH})}_{2}{\text{CuBr}}_{4}$, an unusual antiferromagnetic quantum spin ladder with strong rail interactions that can be saturated in a 30 T field. This transition drives a field-induced color change, a dramatic example of charge-spin coupling in a molecular material. Spin-density calculations reveal that electronic structure is sensitive to the magnetic state because magnetic orbital character depends on the spin arrangement between adjacent ${\text{CuBr}}_{4}^{2\ensuremath{-}}$ chromophores. This finding suggests that molecular architecture and the magnetic arrangement between molecular units might be used to control magnetochromism.}, number={5}, journal={PHYSICAL REVIEW B}, author={White, J. L. and Lee, C. and Gunaydin-Sen, O. and Tung, L. C. and Christen, H. M. and Wang, Y. J. and Turnbull, M. M. and Landee, C. P. and McDonald, R. D. and Crooker, S. A. and et al.}, year={2010}, month={Feb} }
 @article{wu_kan_whangbo_2010, title={On the Importance of the Interplaquette Spin Exchanges in Na3RuO4: Density Functional Theory Analysis of the Spin Exchange and Magnetic Properties}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic902568v}, abstractNote={Na3RuO4 contains layers of high-spin Ru5+ d3 ions grouped into isolated four-membered plaquettes. To determine the spin−lattice appropriate for Na3RuO4, we evaluated the intraplaquette exchanges J1, J2, and J3 as well as the interplaquette exchanges J4 and J5 by performing mapping analysis based on first-principles density functional theory calculations. In addition, we examined how the trends in the calculated J1−J5 are related to the distortions of the RuO6 octahedra in the four-membered plaquettes. The spin−lattice of Na3RuO4 is described by the intraplaquette exchanges J1 and J2 plus the interplaquette exchanges J4 and J5, with spin frustration arising from the (J1, J2, J1) and (J5, J4, J5) triangles. The trends in the calculated J1−J5 reflect the distortions of the RuO6 octahedra in the four-membered plaquettes.}, number={6}, journal={INORGANIC CHEMISTRY}, author={Wu, Fang and Kan, Erjun and Whangbo, Myung-Hwan}, year={2010}, month={Mar}, pages={3025–3028} }
 @article{ji_kan_whangbo_kim_qiu_matsuda_yoshida_hiroi_green_ziman_et al._2010, title={Orbital order and partial electronic delocalization in a triangular magnetic metal Ag2MnO2}, volume={81}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.81.094421}, abstractNote={Magnetic and electrical properties of ${\text{Ag}}_{2}{\text{MnO}}_{2}$ were examined by elastic and inelastic neutron-scattering measurements and by density-functional calculations. The spins of the triangular antiferromagnet metal ${\text{Ag}}_{2}{\text{MnO}}_{2}$ are found to freeze into a gapless short-range collinear state below 50 K because of a ferro-orbital ordering and spin-orbit coupling of the high-spin ${\text{Mn}}^{3+}$ ions. The decrease in the spin-spin correlation lengths of ${\text{Ag}}_{2}{\text{MnO}}_{2}$ in the order, ${\ensuremath{\xi}}_{b}⪢{\ensuremath{\xi}}_{a}⪢{\ensuremath{\xi}}_{c}$, is explained by the spin-exchange interactions calculated for the ferro-orbital ordered state. The electronic states around the Fermi level have significant contributions from the spin-polarized $\text{Mn}\text{ }3d$ and $\text{O}\text{ }2p$ states, which makes electron-electron scattering dominate over electron-phonon scattering at low temperatures leading to the $\ensuremath{\rho}\ensuremath{\propto}{T}^{2}$ behavior below 50 K.}, number={9}, journal={PHYSICAL REVIEW B}, author={Ji, S. and Kan, E. J. and Whangbo, M. -H. and Kim, J. -H. and Qiu, Y. and Matsuda, M. and Yoshida, H. and Hiroi, Z. and Green, M. A. and Ziman, T. and et al.}, year={2010}, month={Mar} }
 @article{kan_xiang_wu_tian_lee_yang_whangbo_2010, title={Prediction for room-temperature half-metallic ferromagnetism in the half-fluorinated single layers of BN and ZnO}, volume={97}, number={12}, journal={Applied Physics Letters}, author={Kan, E. J. and Xiang, H. J. and Wu, F. and Tian, C. and Lee, C. and Yang, J. L. and Whangbo, M. H.}, year={2010} }
 @article{zhang_dai_huang_whangbo_2010, title={Quantum confinement effect on the vacancy-induced spin polarization in carbon, silicon, and germanium nanoparticles: Density functional analysis}, volume={96}, number={6}, journal={Applied Physics Letters}, author={Zhang, Z. K. and Dai, Y. and Huang, B. B. and Whangbo, M. H.}, year={2010} }
 @article{rocquefelte_whangbo_villesuzanne_jobic_tran_schwarz_blaha_2010, title={Short-range magnetic order and temperature-dependent properties of cupric oxide}, volume={22}, number={4}, journal={Journal of Physics. Condensed Matter}, author={Rocquefelte, X. and Whangbo, M. H. and Villesuzanne, A. and Jobic, S. and Tran, F. and Schwarz, K. and Blaha, P.}, year={2010} }
 @article{koo_whangbo_2010, title={Spin dimer and mapping analyses of the magnetic properties of VO(CH3CO2)(2) and VO(OCH2CH2O)}, volume={12}, ISSN={["1293-2558"]}, DOI={10.1016/j.solidstatesciences.2009.03.023}, abstractNote={The spin exchange interactions of VO(CH3CO2)2 and VO(OCH2CH2O) were investigated by performing spin dimer analysis based on tight binding calculations and mapping analysis based on first principles density functional theory calculations. In agreement with experiment, both analyses show that the magnetic properties of VO(CH3CO2)2 and VO(OCH2CH2O) are best described by uniform antiferromagnetic one-dimensional chain and isolated antiferromagnetic dimer models, respectively. Our study shows that the nearest-neighbor spin exchange in the one-dimensional chains of VO5 square pyramids in VO(CH3CO2)2 is mediated by the C 2pπ orbital of the carboxylate group, and that the cis spin dimers of VO(OCH2CH2O) provide strong antiferromagnetic spin exchange than do the trans spin dimers of VO(OCH2CH2O).}, number={5}, journal={SOLID STATE SCIENCES}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2010}, month={May}, pages={685–690} }
 @article{manson_lancaster_blundell_qiu_singleton_sengupta_pratt_kang_lee_whangbo_2010, title={Spin fluctuations and orbital ordering in quasi-one-dimensional alpha-Cu(dca)(2)(pyz) {dca = dicyanamide = N(CN)(2)(-); pyz = pyrazine}, a molecular analogue of KCuF3}, volume={29}, ISSN={["0277-5387"]}, DOI={10.1016/j.poly.2009.06.063}, abstractNote={The magnetic properties of α-Cu(dca)2(pyz) were examined by magnetic susceptibility, magnetization, inelastic neutron scattering (INS), muon-spin relaxation (μSR) measurements and by first-principles density functional theoretical (DFT) calculations and quantum Monte Carlo (QMC) simulations. The χ versus T curve shows a broad maximum at 3.5 K, and the data between 2 and 300 K is well described by an S = 1/2 Heisenberg uniform chain model with g = 2.152(1) and J/kB = −5.4(1) K. μSR measurements, conducted down to 0.02 K and as a function of longitudinal magnetic field, show no oscillations in the muon asymmetry function A(t). This evidence, together with the lack of spin wave formation as gleaned from INS data, suggests that no long-range magnetic order takes place in α-Cu(dca)2(pyz) down to the lowest measured temperatures. Electronic structure calculations further show that the spin exchange is significant only along the Cu–pyz–Cu chains, such that α-Cu(dca)2(pyz) can be described by a Heisenberg antiferromagnetic chain model. Further support for this comes from the M versus B curve, which is strongly concave owing to the reduced spin dimensionality. α-Cu(dca)2(pyz) is a molecular analogue of KCuF3 owing to dx2-y2 orbital ordering where nearest-neighbor magnetic orbital planes of the Cu2+ sites are orthogonal in the planes perpendicular to the Cu–pyz–Cu chains.}, number={1}, journal={POLYHEDRON}, author={Manson, Jamie L. and Lancaster, Tom and Blundell, Stephen J. and Qiu, Yiming and Singleton, John and Sengupta, Pinaki and Pratt, Francis L. and Kang, Jinhee and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2010}, month={Jan}, pages={514–520} }
 @article{gunaydin-sen_lee_tung_chen_turnbull_landee_wang_whangbo_musfeldt_2010, title={Spin-lattice interactions through the quantum critical transition in Cu(pyz)(NO3)(2)}, volume={81}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.81.104307}, abstractNote={We measured the magnetoinfrared response of the quasi-one-dimensional quantum Heisenberg antiferromagnet $\text{Cu}(\text{pyz}){({\text{NO}}_{3})}_{2}$ to investigate local lattice distortions through the field-driven transition to the fully polarized state. This magnetic quantum critical transition involves changes in the out-of-plane N and C-H bending modes of pyrazine with field that directly track the magnetization. We discuss our findings in terms of calculated spin densities, scaling laws, and extracted spin-phonon coupling constants, the latter of which are large due to the softness of the superexchange ligand.}, number={10}, journal={PHYSICAL REVIEW B}, author={Gunaydin-Sen, O. and Lee, C. and Tung, L. C. and Chen, P. and Turnbull, M. M. and Landee, C. P. and Wang, Y. J. and Whangbo, M. -H. and Musfeldt, J. L.}, year={2010}, month={Mar} }
 @article{ben yahia_gaudin_boulahya_darriet_son_whangbo_2010, title={Synthesis and Characterization of the Crystal Structure and Magnetic Properties of the Ternary Manganese Vanadate NaMnVO4}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101180h}, abstractNote={A new ternary manganese vanadate, NaMnVO(4), was synthesized by solid state reaction route, and its crystal structure and magnetic properties were characterized by X-ray diffraction, magnetic susceptibility and specific heat measurements, and by density functional calculations. NaMnVO(4) crystallizes in the maricite-type structure with space group Pnma, a = 9.563(1) A, b = 6.882(1) A, c = 5.316(1) A, and Z = 4. NaMnVO(4) contains MnO(4) chains made up of edge-sharing MnO(6) octahedra, and these chains are interlinked by VO(4) tetrahedra. The magnetic susceptibility has a broad maximum at T(max) = 24 K and follows the Curie-Weiss behavior above 70 K with θ = -62 K. NaMnVO(4) undergoes a three-dimensional antiferromagnetic ordering at T(N) = 11.8 K. The spin exchanges of NaMnVO(4) are dominated by the intrachain antiferromagnetic exchange, and the interchain spin exchanges are spin-frustrated. The most probable magnetic structure of the ordered magnetic state below T(N) was predicted on the basis of the extracted spin exchanges.}, number={18}, journal={INORGANIC CHEMISTRY}, author={Ben Yahia, Hamdi and Gaudin, Etienne and Boulahya, Khalid and Darriet, Jacques and Son, Won-Joon and Whangbo, Myung-Hwan}, year={2010}, month={Sep}, pages={8578–8582} }
 @article{wang_huang_wang_qin_zhang_dai_whangbo_2010, title={Synthesis of Anatase TiO2 Tubular Structures Microcrystallites with a High Percentage of {001} Facets by a Simple One-Step Hydrothermal Template Process}, volume={16}, ISSN={["0947-6539"]}, DOI={10.1002/chem.200903503}, abstractNote={Amazing anatase: Anatase TiO2 tubular structures made up of microcrystallites with a high percentage of {001} facets were synthesized by a simple one-step hydrothermal process with ZrO2 fibers as a template (see graphic). The morphologies, structures and growth procedures were systematically investigated, and a plausible mechanism for the formation of these structures was proposed.}, number={24}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Wang, Xiaoning and Huang, Baibiao and Wang, Zeyan and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2010}, pages={7106–7109} }
 @inproceedings{tong_kremer_kohler_simon_lee_kan_whangbo_2010, title={The layered ferromagnet Cs2AgF4: Antiferromagnetic inter-layer coupling driven by magnetic dipole-dipole interactions}, volume={225}, number={11}, booktitle={Zeitschrift fur Kristallographie}, author={Tong, J. W. and Kremer, R. K. and Kohler, J. and Simon, A. and Lee, C. H. and Kan, E. and Whangbo, M. H.}, year={2010}, pages={498–503} }
 @article{wu_kan_tian_whangbo_2010, title={Theoretical Analysis of the Spin Exchange and Magnetic Dipole-Dipole Interactions Leading to the Magnetic Structure of Ni3TeO6}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101022f}, abstractNote={The origin of the collinear antiferromagnetic magnetic structure of Ni3TeO6 below 52 K was analyzed by calculating its spin exchanges on the basis of density functional calculations, and the cause for the ∥c-spin orientation found for this magnetic structure by calculating the spin−orbit coupling and magnetic dipole−dipole interaction energies. The calculated exchanges correctly predict the observed magnetic structure below 52 K, and lead practically to no spin frustration. The ⊥c- and ∥c-spin orientations are predicted by the spin−orbit coupling and the magnetic dipole−dipole interactions, respectively. However, the magnetic dipole−dipole interactions are stronger than the spin−orbit coupling interactions, and hence are responsible for the spin orientation observed for Ni3TeO6.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Wu, Fang and Kan, Erjun and Tian, Chuan and Whangbo, Myung-Hwan}, year={2010}, month={Aug}, pages={7545–7548} }
 @article{lee_kan_xiang_whangbo_2010, title={Theoretical Investigation of the Magnetic Structure and Ferroelectric Polarization of the Multiferroic Langasite Ba3NbFe3Si2O14}, volume={22}, ISSN={["0897-4756"]}, DOI={10.1021/cm101441p}, abstractNote={The multiferroic langasite Ba3NbFe3Si2O14, crystallizing in a noncentrosymetric space group, has sheets of Fe3+ ions parallel to the ab plane. It adopts a chiral magnetic order below TN = 26 K that has a superstructure with propagation vector (0, 0, ∼1/7). The spin frustration causing this magnetic structure of Ba3NbFe3Si2O14 was examined by evaluating its spin exchange interactions on the basis of density functional calculations and also by calculating its magnetic dipole−dipole interactions. The contribution of the chiral magnetic structure to the ferroelectric polarization of Ba3NbFe3Si2O14 below TN was estimated by Berry phase calculations. The spin exchanges of Ba3NbFe3Si2O14 are frustrated in each //ab sheet and between adjacent sheets of Fe3+ ions. The helical spin rotation along the c axis occurs to minimize the intersheet spin frustration as well as the intersheet magnetic dipole−dipole interactions. The ferroelectric polarization of Ba3NbFe3Si2O14 estimated from calculations is in good agreement with the experimental value.}, number={18}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Kan, Erjun and Xiang, Hongjun and Whangbo, Myung-Hwan}, year={2010}, month={Sep}, pages={5290–5295} }
 @article{xiang_kan_wei_gong_whangbo_2010, title={Thermodynamically stable single-side hydrogenated graphene}, volume={82}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.82.165425}, abstractNote={The single-sided hydrogenation of graphene was examined by combining the cluster expansion method with density-functional theory to find that hydrogen atoms prefer to form one-dimensional chains, leading to ripples made up of $s{p}^{2}$ carbon atoms between them. The formation of such novel structures is due to the competition between electronic kinetic energy and elastic strain energy. Surprisingly, the single-sided hydrogenation of graphene is thermodynamically stable at low hydrogen coverage, and some hydrogenated graphenes are semiconducting, similar to graphene nanoribbons. The new single-side hydrogenated graphene structures account for several puzzling experimental observations. In addition, we propose a low-energy single-side fluorinated graphene structure.}, number={16}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Kan, E. J. and Wei, Su-Huai and Gong, X. G. and Whangbo, M. -H.}, year={2010}, month={Oct} }
 @article{tian_kan_lee_whangbo_2010, title={pi-Back-Donation Effect of the Cyanide Ligands on the Electron Correlation and Charge Transfer in Prussian Blue RbMn[Fe(CN)(6)]}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic902577r}, abstractNote={The temperature-induced charge transfer between the Mn and Fe sites in RbMn[Fe(CN)(6)] was analyzed by density functional theory calculations. Our analysis indicates that the extent of electron correlation (equivalently, the pairing energy or the on-site repulsion) is much greater for the Mn(n+) ion than for the Fe(n+) ion (n = 2, 3). This surprising and counterintuitive finding is a consequence of the pi-back-donation effect of the CN ligands.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Tian, Chuan and Kan, Erjun and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2010}, month={Apr}, pages={3086–3088} }
 @article{xiang_kan_wei_whangbo_yang_2009, title={"Narrow" Graphene Nanoribbons Made Easier by Partial Hydrogenation}, volume={9}, ISSN={["1530-6992"]}, DOI={10.1021/nl902198u}, abstractNote={It is highly desirable to produce narrow-width graphene nanoribbons (GNRs) with smooth edges in large scale. In an attempt to solve this difficult problem, we examined the hydrogenation of GNRs on the basis of first principles density functional calculations. Our study shows that narrow GNRs can be readily obtained from wide GNRs by partial hydrogenation. The hydrogenation of GNRs starts from the edges of GNRs and proceeds gradually toward the middle of the GNRs so as to maximize the number of carbon−carbon π−π bonds, hence effectively leading to narrower GNRs. Furthermore, the partially hydrogenated wide GNRs have similar electronic and magnetic properties as those of the narrow GNRs representing their graphene parts. Therefore, partial hydrogenation of wide GNRs should be a practical and reliable method to produce narrow GNRs in large scale.}, number={12}, journal={NANO LETTERS}, author={Xiang, Hongjun and Kan, Erjun and Wei, Su-Huai and Whangbo, Myung-Hwan and Yang, Jinlong}, year={2009}, month={Dec}, pages={4025–4030} }
 @article{whangbo_koehler_2009, title={A striking transition}, volume={1}, ISSN={["1755-4330"]}, DOI={10.1038/nchem.308}, number={5}, journal={NATURE CHEMISTRY}, author={Whangbo, Myung-Hwan and Koehler, Juergen}, year={2009}, month={Aug}, pages={351–352} }
 @article{wang_huang_qin_zhang_dai_whangbo_2009, title={Ag/AgBr/WO3 center dot H2O: Visible-Light Photocatalyst for Bacteria Destruction}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic9014652}, abstractNote={A new composite photocatalyst Ag/AgBr/WO3·H2O was synthesized by reacting Ag8W4O16 with HBr and then reducing some Ag+ ions in the surface region of AgBr particles to Ag nanoparticles via the light-induced chemical reduction. Ag nanoparticles are formed from AgBr by the light-induced chemical reduction reaction. The Ag/AgBr particles are on the surface of WO3·H2O and have irregular shapes with sizes varying between 63 and 442 nm. WO3·H2O appears as flakes about 31 nm thick and 157−474 nm wide. The as-grown Ag/AgBr/WO3·H2O sample shows strong absorption in the visible region because of the plasmon resonance of Ag nanoparticles in Ag/AgBr/WO3·H2O. The ability of this compound to destroy E. coli and oxidize methylic orange under visible light was compared with those of other reference photocatalysts. Ag/AgBr/WO3·H2O is a highly efficient photocatalyst under visible light. The Ag/AgBr/WO3·H2O samples recovered from repeated photooxidation experiments are almost identical to the as-prepared samples, proving the stability of Ag/AgBr/WO3·H2O sample.}, number={22}, journal={INORGANIC CHEMISTRY}, author={Wang, Peng and Huang, Baibiao and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Whangbo, Myung-Hwan}, year={2009}, month={Nov}, pages={10697–10702} }
 @article{manson_stone_southerland_lancaster_steele_blundell_pratt_baker_mcdonald_sengupta_et al._2009, title={Characterization of the Antiferromagnetism in Ag(pyz)(2)(S2O8) (pyz = Pyrazine) with a Two-Dimensional Square Lattice of Ag2+ Ions}, volume={131}, ISSN={["0002-7863"]}, DOI={10.1021/ja9005223}, abstractNote={X-ray powder diffraction and magnetic susceptibility measurements show that Ag(pyz)(2)(S(2)O(8)) consists of 2D square nets of Ag(2+) ions resulting from the corner-sharing of axially elongated AgN(4)O(2) octahedra and exhibits characteristic 2D antiferromagnetism. Nevertheless, mu(+)SR measurements indicate that Ag(pyz)(2)(S(2)O(8)) undergoes 3D magnetic ordering below 7.8(3) K.}, number={13}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Manson, Jamie L. and Stone, Kevin H. and Southerland, Heather I. and Lancaster, Tom and Steele, Andrew J. and Blundell, Stephen J. and Pratt, Francis L. and Baker, Peter J. and McDonald, Ross D. and Sengupta, Pinaki and et al.}, year={2009}, month={Apr}, pages={4590-+} }
 @article{brinzari_tian_halder_musfeldt_whangbo_schlueter_2009, title={Color Properties and Structural Phase Transition in Penta- And Hexacoordinate Isothiocyanato Ni(II) Compounds}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic802120n}, abstractNote={We investigated the optical properties of (NBu4)3[Ni(NCS)5], a pentacoordinate Ni compound, and compared the results with the more traditional hexacoordinate analogue (NEt4)4[Ni(NCS)6]. On the basis of our complementary electronic structure calculations, the color properties of this high spin complex can be understood in terms of excitations between strongly hybridized orbitals with significant Ni d and ligand character. Variable temperature vibrational studies show mode softening with decreasing temperature and splitting near 200 K, trends that we attribute to improved low temperature intermolecular interactions and a weak structural phase transition, respectively.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Brinzari, T. V. and Tian, C. and Halder, G. J. and Musfeldt, J. L. and Whangbo, M. H. and Schlueter, J. A.}, year={2009}, month={Aug}, pages={7650–7658} }
 @article{reiff_schulz_whangbo_seo_lee_potratz_spicer_girolami_2009, title={Consequences of a Linear Two-Coordinate Geometry for the Orbital Magnetism and Jahn-Teller Distortion Behavior of the High Spin Iron(II) Complex Fe[N(t-Bu)(2)](2)}, volume={131}, ISSN={["0002-7863"]}, DOI={10.1021/ja806660f}, abstractNote={Mossbauer, EPR, magnetic susceptibility, and DFT studies of the unusual two-coordinate iron(II) amide Fe[N(t-Bu)(2)](2) show that it retains a linear N-Fe-N framework due to the nonbonding delta nature of the (xy, x(2)-y(2)) orbitals. The resulting near-degenerate ground state gives rise to a large magnetic moment and a remarkably large internal hyperfine field. The results confirm that extraordinary orbital magnetic effects can arise in linear transition metal complexes in which orbital degeneracies are not broken by Jahn-Teller or Renner-Teller distortions.}, number={2}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Reiff, William M. and Schulz, Charles E. and Whangbo, Myung-Hwan and Seo, Jung In and Lee, Yoon Sup and Potratz, Gregory R. and Spicer, Charles W. and Girolami, Gregory S.}, year={2009}, month={Jan}, pages={404-+} }
 @article{kang_lee_kremer_whangbo_2009, title={Consequences of the intrachain dimer-monomer spin frustration and the interchain dimer-monomer spin exchange in the diamond-chain compound azurite Cu-3(CO3)(2)(OH)(2)}, volume={21}, number={39}, journal={Journal of Physics. Condensed Matter}, author={Kang, J. and Lee, C. and Kremer, R. K. and Whangbo, M. H.}, year={2009} }
 @article{yang_dai_huang_whangbo_2009, title={Density Functional Characterization of the Visible-Light Absorption in Substitutional C-Anion- and C-Cation-Doped TiO2}, volume={113}, ISSN={["1932-7455"]}, DOI={10.1021/jp808483a}, abstractNote={The structural and electronic properties of two possible substitutional carbon-doped structures of anatase and rutile TiO2 [i.e., C for O (C@O)- and C for Ti (C@Ti)-doped TiO2] were studied by performing first-principle density functional theory calculations. In C-doped TiO2 with C@O, the band gap changes slightly, but the doped carbon introduces spin-polarized gap states of C 2p orbital in character. Thus, the associated electron excitations among the valence band, the conduction band, and the gap states explain the various visible-light absorption thresholds observed for C anion-doped TiO2. For C-doped anatase and rutile TiO2 with C@Ti, the doped C atom does not induce spin-polarized states. For C-doped anatase TiO2 with C@Ti, the optical absorption energy is reduced by about 0.18 eV, and the C dopant forms a linear O−C−O unit with short C−O distance resembling carbon dioxide, which is consistent with experiment. In C-doped rutile TiO2 with C@Ti, C-doping reduces the optical absorption energy by about 0.3 eV.}, number={6}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Yang, Kesong and Dai, Ying and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2009}, month={Feb}, pages={2624–2629} }
 @article{lee_kang_lee_whangbo_2009, title={Density Functional Investigation of the Antiferromagnetic Ordering, Spin Orientation, and Ferroelectric Polarization of Rare-Earth Iron Borate TbFe3(BO3)(4)}, volume={21}, ISSN={["1520-5002"]}, DOI={10.1021/cm9006475}, abstractNote={First-principles density functional calculations were carried out to examine the electronic and magnetic properties of rare-earth iron borate TbFe3(BO3)4. The spin exchange interactions between the Fe3+ (d5, S = 5/2) ions and the preferred orientation of the Tb3+ (f8) spins were evaluated, and the ferroelectric polarization of TbFe3(BO3)4 was calculated. In agreement with experiment, our calculations predict that the spin exchange between the Fe3+ spins is ferromagnetic within each //ab sheet of Fe3+ ions but antiferromagnetic between adjacent //ab sheets of Fe3+ ions, whereas the spin exchange between the Fe3+ and Tb3+ ions within each //ab sheet of Fe3+ and Tb3+ ions is antiferromagnetic. The Tb3+ (f8) ions is found to possess an electron configuration responsible for uniaxial magnetism, hence orienting the Tb3+ spins along the c-direction and leading to the highly anisotropic magnetic susceptibility. The ferroelectric polarization of TbFe3(BO3)4 is largely due to the absence of inversion symmetry of the crystal structure and is weakly affected by its magnetic structure.}, number={12}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Kang, Jinhee and Lee, Kee Hag and Whangbo, Myung-Hwan}, year={2009}, month={Jun}, pages={2534–2539} }
 @article{koo_whangbo_2009, title={Density functional investigation of the magnetic properties of PbMBO4 (M = Cr, Mn, Fe)}, volume={149}, ISSN={["1879-2766"]}, DOI={10.1016/j.ssc.2009.01.030}, abstractNote={Mapping analysis based on first principles density functional theory calculations was carried out to examine the spin exchange interactions of PbMBO4 (M=Cr, Mn, Fe), in which chains made up of edge-sharing MO6 octahedra are interconnected by BO3 and PbO4 groups. The dominant spin exchange interaction of PbMBO4 is calculated to be the intra-chain spin exchange, hence predicting a Heisenberg uniform chain model for the description of the magnetic properties of PbMBO4 in agreement with experiment. In reproducing the magnetic properties of PbMBO4, a substantially small on-site repulsion is found necessary for M=Cr compared with that required for M=Mn and Fe.}, number={15-16}, journal={SOLID STATE COMMUNICATIONS}, author={Koo, Hyun Joo and Whangbo, Myung-Hwan}, year={2009}, month={Apr}, pages={602–604} }
 @article{yang_dai_huang_whangbo_2009, title={Density functional studies of the magnetic properties in nitrogen doped TiO2}, volume={481}, ISSN={["0009-2614"]}, DOI={10.1016/j.cplett.2009.09.050}, abstractNote={The ferromagnetic and antiferromagnetic states of anatase and rutile TiO2 doped with N atoms at oxygen sites were investigated by density functional theory calculations for a number of model N-doped TiO2 structures. The each N dopant at an O site exists as an N2− ion with net spin moment of 1.0 μB. In general, the spin exchange coupling between the spin moments of two N dopants is strong when the two dopants are coordinated to a common Ti atom, and whether the coupling between the two N atoms is ferromagnetic or antiferromagnetic in such a case depends on the ∠N–Ti–N angle.}, number={1-3}, journal={CHEMICAL PHYSICS LETTERS}, author={Yang, Kesong and Dai, Ying and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2009}, month={Oct}, pages={99–102} }
 @article{kan_xiang_zhang_lee_whangbo_2009, title={Density-functional analysis of spin exchange and ferroelectric polarization in AgCrO2}, volume={80}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.80.104417}, abstractNote={Density-functional calculations were carried out for ${\text{AgCrO}}_{2}$ to examine its spin exchange and ferroelectric polarization. In the multiferroic state of ${\text{AgCrO}}_{2}$ the triangular spin lattice of each ${\text{CrO}}_{2}$ layer forms parallel chains with helical-spin order. The spin exchange interactions of ${\text{AgCrO}}_{2}$ are strongly frustrated both within and between adjacent ${\text{CuO}}_{2}$ layers, which gives rise to the observed helical-spin order. The observed ferroelectric polarization of ${\text{AgCrO}}_{2}$ is not caused by individual helical-spin chains, but by the spiral-spin chain structures that propagate between the helical-spin chains.}, number={10}, journal={PHYSICAL REVIEW B}, author={Kan, E. J. and Xiang, H. J. and Zhang, Y. and Lee, C. and Whangbo, M. -H.}, year={2009}, month={Sep} }
 @article{koo_xiang_lee_whangbo_2009, title={Effect of Magnetic Dipole-Dipole Interactions on the Spin Orientation and Magnetic Ordering of the Spin-Ladder Compound Sr3Fe2O5}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic9007526}, abstractNote={First-principles density functional theory calculations show that the spin−lattice of Sr3Fe2O5 is practically 2D in terms of its spin-exchange interactions. The magnetic dipole−dipole interactions are found to be essential for the 3D magnetic ordering of Sr3Fe2O5 at a very low temperature.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Xiang, Hongjun and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2009}, month={Oct}, pages={9051–9053} }
 @article{meddar_josse_deniard_la_andre_damay_petricek_jobic_whangbo_maglione_et al._2009, title={Effect of Nonmagnetic Substituents Mg and Zn on the Phase Competition in the Multiferroic Antiferromagnet MnWO4}, volume={21}, ISSN={["1520-5002"]}, DOI={10.1021/cm9021358}, abstractNote={The effects of substituting nonmagnetic Mg2+ and Zn2+ ions for the Mn2+ (S = 5/2) ions on the structural, magnetic, and dielectric properties of the multiferroic frustrated antiferromagnet MnWO4 were investigated. Polycrystalline samples of Mn1−xMgxWO4 and Mn1−xZnxWO4 (0 ≤ x ≤ 0.3) solid solutions were prepared via a solid-state route and characterized via X-ray and neutron diffraction, magnetization, and dielectric permittivity measurements. Mg and Zn substitutions result in very similar effects. The Néel temperature (TN), the AF3-to-AF2 magnetic phase-transition temperature (T2), and the critical ferroelectric temperature (Tc = T2) of MnWO4 are reduced upon nonmagnetic doping. At the lowest temperature (T = 1.5 K), the incommensurate magnetic structure for x(Mg) = 0.15 and x(Zn) = 0.15 corresponds to either a sinusoidal spin arrangement or an elliptical spin-spiral phase similar to the polar AF2 structure observed in MnWO4. These findings were discussed by considering the effects of the Mg and Zn substitutions on the crystal lattice and on the spin exchange network of MnWO4.}, number={21}, journal={CHEMISTRY OF MATERIALS}, author={Meddar, Lynda and Josse, Michael and Deniard, Philippe and La, Carole and Andre, Gilles and Damay, Francoise and Petricek, Vaclav and Jobic, Stephane and Whangbo, Myung-Hwan and Maglione, Mario and et al.}, year={2009}, month={Nov}, pages={5203–5214} }
 @article{jin_dai_huang_whangbo_2009, title={Ferromagnetism of undoped GaN mediated by through-bond spin polarization between nitrogen dangling bonds}, volume={94}, number={16}, journal={Applied Physics Letters}, author={Jin, H. and Dai, Y. and Huang, B. B. and Whangbo, M. H.}, year={2009} }
 @article{zheng_huang_qin_zhang_dai_jiang_wang_whangbo_2009, title={Highly Efficient Photocatalyst: TiO2 Microspheres Produced from TiO2 Nanosheets with a High Percentage of Reactive {001} Facets}, volume={15}, ISSN={["0947-6539"]}, DOI={10.1002/chem.200902438}, abstractNote={Mother sphere superior: Hierarchical TiO2 microspheres (see figure) produced from anatase TiO2 nanosheets with dominant {001} facets (up to 83 %) were synthesized by template- and surfactant-free methods. Compared with Degussa P25, these microspheres possess a superior photocatalytic activity, owing to the high percentage exposure of reactive {001} facets and the porous network of the nanosheets. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={46}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Zheng, Zhaoke and Huang, Baibiao and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Jiang, Minhua and Wang, Peng and Whangbo, Myung-Hwan}, year={2009}, pages={12576–12579} }
 @article{wang_huang_zhang_qin_jin_dai_wang_wei_zhan_wang_et al._2009, title={Highly Efficient Visible-Light Plasmonic Photocatalyst Ag@AgBr}, volume={15}, ISSN={["1521-3765"]}, DOI={10.1002/chem.200802327}, abstractNote={Abstract Visible improvements : Owing to the plasmon resonance of silver nanoparticles deposited on the surface of AgBr, the newly‐prepared plasmonic photocatalyst Ag§AgBr has a strong absorption in the visible region (see picture) and shows high efficiency in the photodegradation of organic pollutants under visible light. magnified image}, number={8}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Wang, Peng and Huang, Baibiao and Zhang, Xiaoyang and Qin, Xiaoyan and Jin, Hao and Dai, Ying and Wang, Zeyan and Wei, Jiyong and Zhan, Jie and Wang, Shaoying and et al.}, year={2009}, pages={1821–1824} }
 @article{mentre_janod_rabu_hennion_leclercq-hugeux_kang_lee_whangbo_petit_2009, title={Incommensurate spin correlation driven by frustration in BiCu2PO6}, volume={80}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.80.180413}, abstractNote={The magnetic properties of ${\text{BiCu}}_{2}{\text{PO}}_{6}$ have been analyzed by means of magnetic-susceptibility and inelastic neutron-scattering measurements on powder samples by evaluating the spin-exchange interactions on the basis of density-functional calculations and by simulating the inelastic neutron scattering in terms of spin-exchange parameters. ${\text{BiCu}}_{2}{\text{PO}}_{6}$ exhibits magnetic properties described by the two-leg spin ladder with strong spin frustration along each leg chain and has a gapped quantum singlet ground state with excited magnetic states, showing an incommensurate dispersion arising from frustration.}, number={18}, journal={PHYSICAL REVIEW B}, author={Mentre, O. and Janod, E. and Rabu, P. and Hennion, M. and Leclercq-Hugeux, F. and Kang, J. and Lee, C. and Whangbo, M. -H. and Petit, S.}, year={2009}, month={Nov} }
 @article{zhang_xiang_whangbo_2009, title={Interplay between Jahn-Teller instability, uniaxial magnetism, and ferroelectricity in Ca3CoMnO6}, volume={79}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.79.054432}, abstractNote={${\text{Ca}}_{3}{\text{CoMnO}}_{6}$ is composed of ${\text{CoMnO}}_{6}$ chains made up of face-sharing ${\text{CoO}}_{6}$ trigonal prisms and ${\text{MnO}}_{6}$ octahedra. The structural, magnetic, and ferroelectric properties of this compound were investigated on the basis of density-functional theory calculations. ${\text{Ca}}_{3}{\text{CoMnO}}_{6}$ is found to undergo a Jahn-Teller distortion associated with the ${\text{CoO}}_{6}$ trigonal prisms containing high-spin ${\text{Co}}^{2+}$ $({d}^{7})$ ions, which removes the ${\text{C}}_{3}$ rotational symmetry and hence uniaxial magnetism. However, the Jahn-Teller distortion is not strong enough to fully quench the orbital moment of the high-spin ${\text{Co}}^{2+}$ ions thereby leading to an electronic state with substantial magnetic anisotropy. The Jahn-Teller distorted ${\text{Ca}}_{3}{\text{CoMnO}}_{6}$ in the magnetic ground state with up-up-down-down spin arrangement is predicted to have electric polarizations much greater than experimentally observed. Implications of the discrepancy between theory and experiment were discussed.}, number={5}, journal={PHYSICAL REVIEW B}, author={Zhang, Y. and Xiang, H. J. and Whangbo, M. -H.}, year={2009}, month={Feb} }
 @article{dessapt_collet_coue_bujoli-doeuff_jobic_lee_whangbo_2009, title={Kinetics of Coloration in Photochromic Organoammonium Polyoxomolybdates}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic8013865}, abstractNote={The excellent photochromic properties of (H2DABCO)2(HDMA)0.5Na0.75(H3O)0.75[Mo8O27]·3H2O (4), a new member of the (H2DABCO)2(A)x[Mo8O27]·nH2O series, are compared with those of (H2DABCO)2(NH4)2[Mo8O27]·4H2O (1), (H2DABCO)2(H2pipz)[Mo8O27] (2), and (H2pipz)3[Mo8O27] (3). All these powdered materials turn from white to purple under illumination at 365 nm, which is associated with photoreduction of Mo6+ cations into Mo5+ cations. We show that the rates of coloration, which increase in the order 1 < 3, 2 < 4, are related to the decrease in the concentration of reducible Mo6+ centers with irradiation time and follow a second-order reaction law because the event of light absorption at a reducible Mo6+ site does not necessarily coincide with that of the N+−H bond breaking in the N+−H···O hydrogen bond associated with the Mo6+ site. First-principles density functional electronic structure calculations were carried out to find that this trend correlates with the homolytic dissociation energies of the N+−H bonds in the organic cations HDMA+, H2pipz2+, H2DABCO2+, and NH4+. This observation is consistent with a photochromic mechanism based on the homolytic cleavage of N+−H bonds rather than on the heterolytic cleavage of N+−H bonds.}, number={2}, journal={INORGANIC CHEMISTRY}, author={Dessapt, Remi and Collet, Mathieu and Coue, Violaine and Bujoli-Doeuff, Martine and Jobic, Stephane and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2009}, month={Jan}, pages={574–580} }
 @article{koehler_simon_whangbo_2009, title={Magnetic Interactions of the 15-Electron Nb6F12 Clusters in Nb6F15}, volume={635}, ISSN={["0044-2313"]}, DOI={10.1002/zaac.200900496}, abstractNote={The crystal structure of Nb6F15 consists of Nb6F12 clusters that are corner-shared through linear Nb–F–Nb bridges to form two simple cubic lattices, which interpenetrate each other with F···F van der Waals contacts only. With 15 valence electrons in Nb–Nb bonding states each cluster carries one unpaired spin. 19F NMR and EPR spectroscopic measurements suggest antiferromagnetic ordering in Nb6F15 below 6 K. A spin-dimer analysis based on tight binding calculations shows that the correct magnetic structure of Nb6F15 associated with this ordering should have the spin arrangement in which two interpenetrating ferromagnetic simple cubic lattices are antiferromagnetically coupled.}, number={15}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Koehler, Juergen and Simon, Arndt and Whangbo, Myung-Hwan}, year={2009}, pages={2396–2398} }
 @article{banks_kremer_hoch_simon_ouladdiaf_broto_rakoto_lee_whangbo_2009, title={Magnetic ordering in the frustrated Heisenberg chain system cupric chloride CuCl2}, volume={80}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.80.024404}, abstractNote={We report a detailed examination of the magnetic structure of anhydrous cupric chloride ${\text{CuCl}}_{2}$ carried out by powder neutron diffraction, magnetic susceptibility, and specific heat measurements on polycrystalline and single-crystal samples as well as an evaluation of the spin-exchange interactions by first-principles density-functional theory (DFT) calculations. Anhydrous ${\text{CuCl}}_{2}$ shows one-dimensional antiferromagnetic behavior and long-range antiferromagnetic ordering below a N\'eel temperature of 23.9 K. Neutron powder and single-crystal diffraction reveal that, below 23.9 K, ${\text{CuCl}}_{2}$ undergoes a phase transition into an incommensurate magnetic structure [propagation vector (1,0.2257,0.5) with a spin spiral propagating along $b$ and the moments confined in the $bc$ crystallographic plane]. Our DFT calculations show that the spin spiral results from competing ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor spin-exchange interactions along the spin chains. Implications for possible multiferroic behavior of ${\text{CuCl}}_{2}$ are discussed.}, number={2}, journal={PHYSICAL REVIEW B}, author={Banks, M. G. and Kremer, R. K. and Hoch, C. and Simon, A. and Ouladdiaf, B. and Broto, J. -M. and Rakoto, H. and Lee, C. and Whangbo, M. -H.}, year={2009}, month={Jul} }
 @article{wu_kan_xiang_wei_whangbo_yang_2009, title={Magnetic states of zigzag graphene nanoribbons from first principles}, volume={94}, number={22}, journal={Applied Physics Letters}, author={Wu, F. and Kan, E. J. and Xiang, H. J. and Wei, S. H. and Whangbo, M. H. and Yang, J. L.}, year={2009} }
 @article{tian_lee_xiang_zhang_payen_jobic_whangbo_2009, title={Magnetic structure and ferroelectric polarization of MnWO4 investigated by density functional calculations and classical spin analysis}, volume={80}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.80.104426}, abstractNote={The ordered magnetic states of MnWO4 at low temperatures were examined by evaluating the spin exchange interactions between the Mn2+ ions of MnWO4 on the basis of first principles density functional calculations and by performing classical spin analysis with the resulting spin exchange parameters. Our work shows that the spin exchange interactions are frustrated within each zigzag chain of Mn2+ ions along the c-direction and between such chains of Mn2+ ions along the a-direction. This explains the occurrence of a spiral-spin order along the c- and a-directions in the incommensurate magnetic state AF2, and that of a uudd spin order along the c- and a-directions in the commensurate magnetic state AF1. The ferroelectric polarization of MnWO4 in the spiral-spin state AF2 was examined by performing Berry phase calculations for a model superstructure to find that the ferroelectric polarization occurs along the b-direction, in agreement with experiment.}, number={10}, journal={PHYSICAL REVIEW B}, author={Tian, Chuan and Lee, Changhoon and Xiang, Hongjun and Zhang, Yuemei and Payen, Christophe and Jobic, Stephane and Whangbo, Myung-Hwan}, year={2009}, month={Sep} }
 @article{kan_xiang_yang_whangbo_2009, title={Magnetism of semiconductor-based magnetic tunnel junctions under electric field from first principles}, volume={94}, number={25}, journal={Applied Physics Letters}, author={Kan, E. J. and Xiang, H. J. and Yang, J. L. and Whangbo, M. H.}, year={2009} }
 @article{musfeldt_vergara_brinzari_lee_tung_kang_wang_schlueter_manson_whangbo_2009, title={Magnetoelastic Coupling through the Antiferromagnet-to-Ferromagnet Transition of Quasi-Two-Dimensional [Cu(HF2)(pyz)(2)]BF4 Using Infrared Spectroscopy}, volume={103}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.103.157401}, abstractNote={We investigated magnetoelastic coupling through the field-driven transition to the fully polarized magnetic state in quasi-two-dimensional $[\mathrm{Cu}({\mathrm{HF}}_{2})(\mathrm{pyz}{)}_{2}]{\mathrm{BF}}_{4}$ by magnetoinfrared spectroscopy. This transition modifies out-of-plane ring distortion and bending vibrational modes of the pyrazine ligand. The extent of these distortions increases with the field, systematically tracking the low-temperature magnetization. These distortions weaken the antiferromagnetic spin exchange, a finding that provides important insight into magnetic transitions in other copper halides.}, number={15}, journal={PHYSICAL REVIEW LETTERS}, author={Musfeldt, J. L. and Vergara, L. I. and Brinzari, T. V. and Lee, C. and Tung, L. C. and Kang, J. and Wang, Y. J. and Schlueter, J. A. and Manson, J. L. and Whangbo, M. -H.}, year={2009}, month={Oct} }
 @article{xiang_kan_wei_whangbo_yang_2009, title={Origin of the Ising ferrimagnetism and spin-charge coupling in LuFe2O4}, volume={80}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.80.132408}, abstractNote={The spin-ordering and spin-charge coupling in ${\text{LuFe}}_{2}{\text{O}}_{4}$ were investigated on the basis of density functional calculations and Monte Carlo simulations. The 2:1 ferrimagnetism arises from the strong antiferromagnetic intrasheet ${\text{Fe}}^{3+}{\text{-Fe}}^{3+}$ and ${\text{Fe}}^{3+}{\text{-Fe}}^{2+}$ as well as some substantial antiferromagnetic ${\text{Fe}}^{2+}{\text{-Fe}}^{3+}$ intersheet spin exchange interactions. The giant magnetocapacitance at room temperature and the enhanced electric polarization at 240 K of ${\text{LuFe}}_{2}{\text{O}}_{4}$ are explained by the strong spin-charge coupling.}, number={13}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Kan, E. J. and Wei, Su-Huai and Whangbo, M. -H. and Yang, Jinlong}, year={2009}, month={Oct} }
 @article{liu_huang_dai_zhang_qin_jiang_whangbo_2009, title={Selective ethanol formation from photocatalytic reduction of carbon dioxide in water with BiVO4 photocatalyst}, volume={11}, ISSN={["1873-3905"]}, DOI={10.1016/j.catcom.2009.10.010}, abstractNote={The visible-light responsive photocatalyst BiVO4 was synthesized, and its photocatalytic reduction of CO2 in water was examined. Our study shows the selective formation of ethanol under the condition of high intensity visible-light irradiation, and suggests that intense irradiation generates a large number of C1 intermediate species anchored on the surface of BiVO4, which dimerize to form ethanol. For the photocatalytic reduction of CO2 into ethanol, monoclinic BiVO4 is more efficient than tetragonal BiVO4.}, number={3}, journal={CATALYSIS COMMUNICATIONS}, author={Liu, Yuanyuan and Huang, Baibiao and Dai, Ying and Zhang, Xiaoyang and Qin, Xiaoyan and Jiang, Minhua and Whangbo, Myung-Hwan}, year={2009}, month={Nov}, pages={210–213} }
 @article{denis_rocquefelte_deniard_whangbo_jobic_2009, title={Site preference of Eu2+ dopants in the (Ba,Sr)(13-x)Al22-2xSi10+2xO66 phosphor and its effect on the luminescence properties: a density functional investigation}, volume={19}, ISSN={["1364-5501"]}, DOI={10.1039/b914374b}, abstractNote={First principles density functional calculations were carried out for model compounds Ba12EuAl22Si10O66 and Sr12EuAl22Si10O66 to account for the luminescence properties of Eu2+ doped Ba13−xAl22−2xSi10+2xO66 and Eu2+ doped (Ba,Sr)13−xAl22−2xSi10+2xO66. Both host lattices have three different crystallographic alkaline earth sites, namely, AE(1), AE(2) and AE(3), at which the dopants Eu2+ are located. The fluorescence properties of Eu2+ doped Ba13−xAl22−2xSi10+2xO66 are not explained if the dopant ions Eu2+ are considered to randomly occupy the three different Ba sites, but are explained if the dopants are considered to preferentially occupy the Ba(3) sites. In contrast, the fluorescence properties of Eu2+ doped (Ba,Sr)13−xAl22−2xSi10+2xO66 are explained only when both Sr2+ and Eu2+ cations are considered to occupy the AE(3) sites, which suggests that the activators are more randomly distributed over the three AE sites in Eu2+ doped (Ba,Sr)13−xAl22−2xSi10+2xO66 than in Eu2+ doped Ba13−xAl22−2xSi10+2xO66. Calculations evidence the strong tendency for the Ba(3) sites to accommodate defects in Ba13−xAl22−2xSi10+2xO66, namely, Eu dopants, Sr substituents, and Ba vacancies. This arises from the higher malleability of the Ba(3) site compared to the Ba(1) and Ba(2) sites.}, number={48}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Denis, Gregoire and Rocquefelte, Xavier and Deniard, Philippe and Whangbo, Myung-Hwan and Jobic, Stephane}, year={2009}, pages={9170–9175} }
 @article{manson_schlueter_funk_southerland_twamley_lancaster_blundell_baker_pratt_singleton_et al._2009, title={Strong H center dot center dot center dot F Hydrogen Bonds as Synthons in Polymeric Quantum Magnets: Structural, Magnetic, and Theoretical Characterization of [Cu(HF2)(pyrazine)(2)]SbF6, [Cu2F(HF)(HF2)(pyrazine)(4)](SbF6)(2), and [CuAg(H3F4)(pyrazine)(5)](SbF6)(2)}, volume={131}, ISSN={["1520-5126"]}, DOI={10.1021/ja808761d}, abstractNote={Three Cu(2+)-containing coordination polymers were synthesized and characterized by experimental (X-ray diffraction, magnetic susceptibility, pulsed-field magnetization, heat capacity, and muon-spin relaxation) and electronic structure studies (quantum Monte Carlo simulations and density functional theory calculations). [Cu(HF(2))(pyz)(2)]SbF(6) (pyz = pyrazine) (1a), [Cu(2)F(HF)(HF(2))(pyz)(4)](SbF(6))(2) (1b), and [CuAg(H(3)F(4))(pyz)(5)](SbF(6))(2) (2) crystallize in either tetragonal or orthorhombic space groups; their structures consist of 2D square layers of [M(pyz)(2)](n+) that are linked in the third dimension by either HF(2)(-) (1a and 1b) or H(3)F(4)(-) (2). The resulting 3D frameworks contain charge-balancing SbF(6)(-) anions in every void. Compound 1b is a defective polymorph of 1a, with the difference being that 50% of the HF(2)(-) links are broken in the former, which leads to a cooperative Jahn-Teller distortion and d(x(2))(-y(2)) orbital ordering. Magnetic data for 1a and 1b reveal broad maxima in chi at 12.5 and 2.6 K and long-range magnetic order below 4.3 and 1.7 K, respectively, while 2 displays negligible spin interactions owing to long and disrupted superexchange pathways. The isothermal magnetization, M(B), for 1a and 1b measured at 0.5 K reveals contrasting behaviors: 1a exhibits a concave shape as B increases to a saturation field, B(c), of 37.6 T, whereas 1b presents an unusual two-step saturation in which M(B) is convex until it reaches a step near 10.8 T and then becomes concave until saturation is reached at 15.8 T. The step occurs at two-thirds of M(sat), suggesting the presence of a ferrimagnetic structure. Compound 2 shows unusual hysteresis in M(B) at low temperature, although chi vs T does not reveal the presence of a magnetic phase transition. Quantum Monte Carlo simulations based on an anisotropic cubic lattice were applied to the magnetic data of 1a to afford g = 2.14, J = -13.4 K (Cu-pyz-Cu), and J(perpendicular) = -0.20 K (Cu-F...H...F-Cu), while chi vs T for 1b could be well reproduced by a spin-1/2 Heisenberg uniform chain model for g = 2.127(1), J(1) = -3.81(1), and zJ(2) = -0.48(1) K, where J(1) and J(2) are the intra- and interchain exchange couplings, respectively, which considers the number of magnetic nearest-neighbors (z). The M(B) data for 1b could not be satisfactorily explained by the chain model, suggesting a more complex magnetic structure in the ordered state and the need for additional terms in the spin Hamiltonian. The observed variation in magnetic behaviors is driven by differences in the H...F hydrogen-bonding motifs.}, number={19}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Manson, Jamie L. and Schlueter, John A. and Funk, Kylee A. and Southerland, Heather I. and Twamley, Brendan and Lancaster, Tom and Blundell, Stephen J. and Baker, Peter J. and Pratt, Francis L. and Singleton, John and et al.}, year={2009}, month={May}, pages={6733–6747} }
 @article{lee_kang_lee_whangbo_2009, title={Symmetry-Dependent Strong Reduction of the Spin Exchange Interactions in Cs2CuCl4 by the 6p Orbitals of Cs+ Ions}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic802412x}, abstractNote={Despite a three-dimensional arrangement of its CuCl42− ions, the magnetic properties of Cs2CuCl4 are explained by a two-dimensional frustrated triangular antiferromagnetic spin−lattice. The origin of this low-dimensional magnetism was explored by evaluating the spin exchange interactions of A2CuCl4 (A = Cs, Rb, K, Na) on the basis of first principles density functional calculations. The calculated spin exchange parameters agree with experiment only when the Cs+ ions located between the CuCl42− ions are not neglected. The antiferromagnetic spin exchange interaction between adjacent CuCl42− ions is strongly reduced by the 6p orbitals of the intervening Cs+ ions when the arrangement of the CuCl42− and Cs+ ions has either mirror-plane or inversion symmetry. The observed magnetism of Cs2CuCl4 arises from this symmetry-dependent participation of the 6p orbitals of the Cs+ ions in the spin exchange interactions between CuCl42− ions.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Lee, Changhoon and Kang, Jinhee and Lee, Kee Hag and Whangbo, Myung-Hwan}, year={2009}, month={May}, pages={4165–4170} }
 @article{he_wangbo_ueda_narumi_kindo_taniyama_itoh_cheng_2009, title={Synthesis and Magnetic Properties of Ba2Mn2Si2O9: the First Example of S=2 Spin-Dimer with Spin-Singlet Ground}, volume={4}, ISSN={["1861-471X"]}, DOI={10.1002/asia.200900235}, abstractNote={Correlation of structure and property: Ba2Mn2Si2O9 consists of Mn2O8 dimers made up of two basal-edge-sharing MnO5 square pyramids. Magnetic measurements show that this material displays a spin-singlet ground state with a large spin gap. The spin-dimer analysis suggests that the origin of the spin gap is likely to arise from a large intra-dimer interaction between the Mn1O5 and Mn2O5 square pyramids. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={10}, journal={CHEMISTRY-AN ASIAN JOURNAL}, author={He, Zhangzhen and Wangbo, Myung-Hwan and Ueda, Yutaka and Narumi, Yasuo and Kindo, Koichi and Taniyama, Tomoyasu and Itoh, Mitsuru and Cheng, Wendan}, year={2009}, pages={1530–1535} }
 @article{wang_huang_qin_zhang_dai_wei_whangbo_2008, title={Ag@AgCl: A highly efficient and stable photocatalyst active under visible light}, volume={47}, ISSN={["1521-3773"]}, DOI={10.1002/anie.200802483}, abstractNote={Plasmonic photocatalyst [email protected], in which Ag nanoparticles are deposited on the surfaces of AgCl particles (SEM image depicted), was prepared by treating Ag2MoO4 with HCl to form AgCl powder and then reducing some Ag+ ions in the surface region of the AgCl particles to Ag0. This photocatalyst is highly efficient, for example in the degradation of organic dyes, and stable under visible light.}, number={41}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Wang, Peng and Huang, Baibiao and Qin, Xiaoyan and Zhang, Xiaoyang and Dai, Ying and Wei, Jiyong and Whangbo, Myung-Hwan}, year={2008}, pages={7931–7933} }
 @article{lee_whangbo_koehler_2008, title={Analysis of electronic structures and chemical bonding of metal-rich compounds. I. Density functional study of Pt metal, LiPt2, LiPt, and Li2Pt}, volume={29}, ISSN={["1096-987X"]}, DOI={10.1002/jcc.21020}, abstractNote={First principles density functional theory calculations were carried out for the series of metal-rich compounds, LiPt2, LiPt, and Li2Pt, and elemental Pt for comparison, to probe the bonding picture that captures the essence of their electronic structures. Our analysis shows that the 5d-electron configuration of Pt in these compounds is close to (5d)10, and the electrons released from the Li atoms in the Li/Pt binary compounds are delocalized among the Pt0 atoms and Li+ ions through the interactions of the Pt 5d orbitals of each Pt with the Pt 6s/6p of neighboring Pt atoms and the Li 2s/2p orbitals of neighboring Li atoms. The electron counting schemes best representing the electronic structures of Pt metal, LiPt2, LiPt and Li2Pt are Pt0 (d10), Li+[Pt0 (d10)]2(e−), Li+[Pt0 (d10)](e−), and (Li+)2[Pt0 (d10)](2e−), respectively, and hence the Pt atoms of the Li/Pt binary compounds are predicted to exist as partially negative anions. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008}, number={13}, journal={JOURNAL OF COMPUTATIONAL CHEMISTRY}, author={Lee, Changhoon and Whangbo, Myung-Hwan and Koehler, Juergen}, year={2008}, month={Oct}, pages={2154–2160} }
 @article{koo_whangbo_2008, title={Analysis of the spin lattice model for the spin-gapped layered compounds Na3Cu2SbO6 and Na2Cu2TeO6 on the basis of electronic structure calculations}, volume={47}, ISSN={["1520-510X"]}, DOI={10.1021/ic701153z}, abstractNote={The spin lattice model for the spin-gapped layered magnetic solids Na3Cu2SbO6 and Na2Cu2TeO6 was examined by evaluating the three spin exchange interactions of their Cu2MO6 (M = Sb, Te) layers in terms of spin dimer analysis based on extended Hückel tight binding calculations and mapping analysis based on first principles density functional theory electronic band structure calculations. For both compounds, our calculations show that the two strongest spin exchange interactions, that is, the Cu−O···O−Cu super-superexchange (J2) and the Cu−O−Cu superexchange (J1) interactions, form alternating chains that interact weakly through the Cu−O−Cu superexchange (J3) interactions. The dominant one of the three spin exchange interactions is J2, and it is antiferromagnetic in agreement with the fact that both of the compounds are spin gapped. For Na3Cu2SbO6 and Na2Cu2TeO6, the superexchange J1 is calculated to be ferromagnetic, hence, leading to the alternating chain model in which antiferromagnetic and ferromagnetic spin exchange interactions alternate. This picture does not agree with the recent experimental analysis, which showed that the temperature-dependent magnetic susceptibilities of both compounds should be described by the alternating chain model in which two antiferromagnetic spin exchange interactions of different strengths alternate.}, number={1}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2008}, month={Jan}, pages={128–133} }
 @article{liu_dronskowski_kremer_ahrens_lee_whangbo_2008, title={Characterization of the magnetic and structural properties of copper carbodiimide, CuNCN, by neutron diffraction and first-principles evaluations of its spin exchange interactions}, volume={112}, ISSN={["1932-7447"]}, DOI={10.1021/jp8007199}, abstractNote={The crystal structure of copper carbodiimide, CuNCN, was determined from neutron diffraction data at room temperature and at 4 K, and the electrical resistivity, specific heat, and magnetic susceptibility measurements were carried out. The spin exchange interactions of CuNCN were evaluated by performing first-principles density functional theory electronic structure calculations. CuNCN is a semiconductor containing Jahn−Teller distorted CuN6 octahedra around the divalent copper ions, and the material shows a very small and almost temperature-independent magnetic susceptibility. Our electronic structure calculations evidence that the spin exchange interactions of CuNCN are dominated by two antiferromagnetic spin exchange paths leading to a triangular lattice antiferromagnet within the ab plane. Because the coupling between the layers (along the c axis) is small, CuNCN may be regarded a two-dimensional S = 1/2 frustrated triangular Heisenberg quantum antiferromagnet.}, number={29}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Liu, Xiaohui and Dronskowski, Richard and Kremer, Reinhard K. and Ahrens, Martin and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2008}, month={Jul}, pages={11013–11017} }
 @article{angst_hermann_christianson_lumsden_lee_whangbo_kim_ryan_nagler_tian_et al._2008, title={Charge Order in LuFe2O4: Antiferroelectric Ground State and Coupling to Magnetism}, volume={101}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.101.227601}, abstractNote={X-ray scattering by multiferroic LuFe2O4 is reported. Below 320 K, superstructure reflections indicate an incommensurate charge order with propagation close to (1/3 1/3 3/2). The corresponding charge configuration, also found by electronic structure calculations as most stable, contains polar Fe/O double layers with antiferroelectric stacking. Diffuse scattering at 360 K, with (1/3 1/3 0) propagation, indicates ferroelectric short-range correlations between neighboring double layers. The temperature dependence of the incommensuration indicates that charge order and magnetism are coupled.}, number={22}, journal={PHYSICAL REVIEW LETTERS}, author={Angst, M. and Hermann, R. P. and Christianson, A. D. and Lumsden, M. D. and Lee, C. and Whangbo, M. -H. and Kim, J. -W. and Ryan, P. J. and Nagler, S. E. and Tian, W. and et al.}, year={2008}, month={Nov} }
 @article{wang_huang_zhang_qin_dai_jin_wei_whangbo_2008, title={Composite semiconductor H2WO4 center dot H2O/AgCl as an efficient and stable photocatalyst under visible light}, volume={14}, number={34}, journal={Chemistry (Weinheim An Der Bergstrasse, Germany)}, author={Wang, P. and Huang, B. B. and Zhang, X. Y. and Qin, X. Y. and Dai, Y. and Jin, H. and Wei, J. Y. and Whangbo, M. H.}, year={2008}, pages={10543–10546} }
 @article{yang_dai_huang_whangbo_2008, title={Density Functional Characterization of the Band Edges, the Band Gap States, and the Preferred Doping Sites of Halogen-Doped TiO2}, volume={20}, ISSN={["1520-5002"]}, DOI={10.1021/cm801741m}, abstractNote={First-principles density functional theory (DFT) electronic structure calculations were carried out for model halogen-doped anatase TiO2 structures to evaluate the effect of halogen doping on the band edges and the photocatalytic activity of TiO2. The model structures of X-doped TiO2 were constructed by using the 48-atom 2 × 2 × 1 supercell of anatase TiO2 with one O or one Ti atom replaced with X (=F, Cl, Br, I). The unit cell parameters and the atom positions of the resulting X-doped TiO2 with X at an O site (X@O) and that with X at a Ti site (X@Ti) were optimized by performing first-principles DFT calculations. On the basis of the optimized structures of X-doped TiO2 with X@O and X@Ti, the defect formation energies and the plots of the density of states were calculated to analyze the band edges, the band gap states, and the preferred doping sites. Our work shows that the doping becomes more difficult in the order F < Cl < Br < I for X-doped TiO2 with X@O, while the doping becomes less difficult in the order F < Cl < Br < I for X-doped TiO2 with X@Ti. Under O-rich growth condition, it is energetically more favorable to substitute Br and I for a Ti site than for an O site, while it is energetically more favorable to substitute F and Cl for an O site than for a Ti site. Under Ti-rich condition, it is energetically more favorable to substitute all X (=F, Cl, Br, I) for an O site than for a Ti site. The I atoms in I-doped TiO2 with I@Ti are present as I5+ (s2) ions, while in X-doped TiO2 with X@Ti (X = F, Cl, Br) the F, Cl, and Br are present as F3+ (s2p2), Cl4+ (s2p1), and Br4+ (s2p1) ions, respectively. I-doped TiO2 either with I@Ti or with I@O has a doubly filled band gap state, which significantly reduces the optical band gap with respect to that of undoped TiO2.}, number={20}, journal={CHEMISTRY OF MATERIALS}, author={Yang, Kesong and Dai, Ying and Huang, Baibiao and Whangbo, Myung-Hwan}, year={2008}, month={Oct}, pages={6528–6534} }
 @article{koo_whangbo_2008, title={Determination of the spin-lattice relevant for the quaternary magnetic oxide Bi4Cu3V2O14 on the basis of tight-binding and density functional calculations}, volume={47}, ISSN={["1520-510X"]}, DOI={10.1021/ic800216j}, abstractNote={The quaternary magnetic oxide Bi4Cu3V2O14 consists of Cu4O8 triple chains made up of corner-sharing CuO4 square planes. To determine its spin-lattice, the spin exchange interactions of Bi4Cu3V2O14 were evaluated by performing a spin dimer analysis based on tight-binding calculations and a mapping analysis based on first principles density functional theory calculations. Both calculations show that the spin-lattice of Bi4Cu3V2O14 is not an antiferromagnetically coupled diamond chain, which results from an idealized view of the structure of the Cu4O8 triple chain and a neglect of super-superexchange interactions. The correct spin-lattice is an antiferromagnetic chain made up of antiferromagnetic linear trimers coupled through their midpoints via super-superexchange interaction, which predicts that Bi4Cu3V2O14 has an antiferromagnetic spin ground state and has no spin frustration, both in agreement with experiment.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2008}, month={Jun}, pages={4779–4784} }
 @article{dai_xiang_whangbo_2008, title={Effects of spin-orbit coupling on magnetic properties of discrete and extended magnetic systems}, volume={29}, ISSN={["0192-8651"]}, DOI={10.1002/jcc.21011}, abstractNote={In accounting for the magnetic properties of discrete and extended compounds with unpaired spins, it is crucial to know the nature of their ground and low-lying excited states. In this review we surveyed quantum mechanical descriptions on how these states are affected by spin-orbit coupling and attempted to provide a conceptual framework with which to think about spin-orbit coupling and its applications.}, number={13}, journal={JOURNAL OF COMPUTATIONAL CHEMISTRY}, author={Dai, Dadi and Xiang, Hongjun and Whangbo, Myung-Hwan}, year={2008}, month={Oct}, pages={2187–2209} }
 @article{koehler_whangbo_2008, title={Electronic structure study of the [Ag-Ag](4-), [Au-Au](4-), and [Hg-Hg](2-) zintl anions in the intermetallic compounds Yb3Ag2, Ca5Au4, and Ca3Hg2: Transition metal anions as p-metal elements}, volume={20}, ISSN={["1520-5002"]}, DOI={10.1021/cm703590d}, abstractNote={The chemical bonding of the M2 dimers (M = Ag, Au, Hg) present in Yb3Ag2, Ca5Au4 and Ca3Hg2 was examined on the basis of first principles electronic band structure calculations. In these compounds, the 6s- and 5d-block bands of M are completely filled while the frontier levels of M are given by partially filled 6p-block bands such that the transition metal atoms M are best described as anions with electron configuration (5d)10(6s)2(6p)1. Thus, the M2 dimers (M = Ag, Au, Hg) of Yb3Ag2, Ca5Au4 and Ca3Hg2 are present as [Ag−Ag]4−, [Au−Au]4−, and [Hg−Hg]2− Zintl-anions, respectively, in these compounds in which the M2 dimers have a single bond formed by the pσ−pσ interaction between the 5p and 6p orbitals of M atoms. The anions of late transition metal elements are different from those of late main group elements in their tendency for covalent bond formation.}, number={8}, journal={CHEMISTRY OF MATERIALS}, author={Koehler, Juergen and Whangbo, Myung-Hwan}, year={2008}, month={Apr}, pages={2751–2756} }
 @article{wang_huang_yu_dai_wang_qin_zhang_wei_zhan_jing_et al._2008, title={Enhanced Ferromagnetism and Tunable Saturation Magnetization of Mn/C-Codoped GaN Nanostructures Synthesized by Carbothermal Nitridation}, volume={130}, ISSN={["0002-7863"]}, DOI={10.1021/ja807030v}, abstractNote={Mn/C-codoped GaN nanostructures were synthesized by carbothermal nitridation with active charcoal as the carbon source. Nanostructures such as zigzag nanowires and nanoscrews were observed by varying the reaction time and the C/Ga molar ratio of the starting material used for the synthesis. The structures and morphologies of the as-grown samples were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy measurements. The doping of both Mn and C in the GaN matrix was confirmed by X-ray photoelectron spectroscopy measurements, and the ferromagnetic properties of Mn/C-codoped GaN samples were confirmed by room-temperature magnetization measurements. The saturation magnetization of Mn/C-codoped GaN increases steadily with increasing C/Ga molar ratio of the starting material at a rate of ∼0.023 emu/g per C/Ga molar ratio, and the ferromagnetism of Mn/C-codoped GaN can be stronger than that of Mn-doped GaN by a factor of ∼40. A plausible growth mechanism was proposed, and the role of carbon codoping in tuning the morphology and ferromagnetic property was discussed. Our work suggests that carbon doping in the GaN matrix favors the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping strongly enhances the preference of the FM coupling to the AFM coupling between the two doped Mn sites. These suggestions were probed on the basis of first-principles density functional theory electronic structure calculations for a number of model doped structures constructed with a 32-atom 2 × 2 × 2 supercell.}, number={48}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Wang, Zeyan and Huang, Baibiao and Yu, Lin and Dai, Ying and Wang, Peng and Qin, Xiaoyan and Zhang, Xiaoyang and Wei, Jiyong and Zhan, Jie and Jing, Xiangyang and et al.}, year={2008}, month={Dec}, pages={16366–16373} }
 @article{manson_conner_schlueter_mcconnell_southerland_malfant_lancaster_blundell_brooks_pratt_et al._2008, title={Experimental and Theoretical Characterization of the Magnetic Properties of CuF2(H2O)(2)(pyz) (pyz = pyrazine): A Two-Dimensional Quantum Magnet Arising from Supersuperexchange Interactions through Hydrogen Bonded Paths}, volume={20}, ISSN={["1520-5002"]}, DOI={10.1021/cm8016566}, abstractNote={The structural, electronic, and magnetic properties of the new linear chain coordination polymer CuF2(H2O)2(pyz) (pyz = pyrazine) were determined by single crystal X-ray diffraction at various temperatures, SQUID magnetometry, pulsed-field magnetization, ESR, muon-spin relaxation (μSR), and electronic structure calculations. Each Cu2+ ion of CuF2(H2O)2(pyz) is located at a distorted CuF2O2N2 octahedron with axial elongation along the Cu−N bonds. These octahedra are tethered together by strong F···H−O hydrogen bonds to yield two-dimensional (2D) square nets in the bc-plane that are linked along the a-direction by pyrazine linkages. Measurements of the g-factor by ESR along with first principles density functional theory electronic structure calculations show that the magnetic orbital of the Cu2+ ion lies in the CuF2O2 plane thus forming a 2D antiferromagnetic square lattice. A broad maximum observed in χ(T) at 10 K indicates a modest spin exchange interaction through the Cu−F···H−O−Cu supersuperexchange paths, and a theoretical fit of χ(T) to a 2D square model gives J2D/kB = −5.58(1) K (in the convention where J rather than 2J is used for spin exchange). At lower temperatures, χ(T) shows a sharp peak at ∼2.6 K, which signals a transition to a long-range magnetic ordering as confirmed by coherent precession of implanted muons. Isothermal M(B) measurements made at 0.5 K on an aligned single crystal reveal magnetic saturation, Msat, at 28.8 T (B∥a) while a higher field of 33.1 T is required to saturate the spins when B is applied perpendicular to the a-axis thus showing clear anisotropy in these orientations. The presence of strong hydrogen bonds in CuF2(H2O)2(pyz) causes the chains to adopt a tilted packing arrangement, thus leading to a novel ground-state likely characterized by spin-canting within the 2D layers and a markedly increased critical temperature relative to the well-known Cu(NO3)2(pyz) polymer chain compound.}, number={24}, journal={CHEMISTRY OF MATERIALS}, author={Manson, Jamie L. and Conner, Marianne M. and Schlueter, John A. and McConnell, Amber C. and Southerland, Heather I. and Malfant, Isabelle and Lancaster, Tom and Blundell, Stephen J. and Brooks, Michael L. and Pratt, Francis L. and et al.}, year={2008}, month={Dec}, pages={7408–7416} }
 @article{mentre_koo_whangbo_2008, title={Investigation of the Vanadyl Bond Ordering and Analysis of the Spin Exchange Interactions in Pb2V3O9 and Pb(2)AS(2)VO(9)}, volume={20}, ISSN={["0897-4756"]}, DOI={10.1021/cm800924j}, abstractNote={The structures of Pb2V3O9 and Pb2As2VO9 were determined by X-ray diffraction to settle the issue concerning whether the arrangement of the V4+═O vanadyl bonds is ordered or disordered. The new crystal structure of Pb2V3O9 refined by using a twinned crystal differs from the previous structure, determined from a combined use of powder X-ray and neutron diffraction data, and suggests an ordered Ferro arrangement of the V4+═O vanadyl bonds as does the Antiferro crystal structure of the new Pb2As2VO9. In Pb2V3O9, a triclinic → monoclinic transition is observed at 400 °C, and the corresponding high temperature form was structurally characterized. The spin exchange interactions of Pb2V3O9 and Pb2As2VO9 were evaluated by performing qualitative spin dimer analysis based on tight binding calculations, and those of Pb2V3O9 were also examined by quantitative mapping analysis based on density functional theory calculations. To a first approximation, the spin−lattice of Pb2V3O9 is described by an alternating antiferromagnetic chain model, which is made up of the super-superexchange interactions mediated by VO4 tetrahedra between adjacent chains of corner-sharing V4+O6 octahedra. The magnetic property of Pb2As2VO9 is predicted to be paramagnetic, in agreement with experiment.}, number={22}, journal={CHEMISTRY OF MATERIALS}, author={Mentre, O. and Koo, H. J. and Whangbo, M. -H.}, year={2008}, month={Nov}, pages={6929–6938} }
 @article{suh_park_kang_hwang_jung_kim_lee_whangbo_2008, title={Investigation of the scanning tunneling microscopy image, the stacking pattern and the bias-voltage dependent structural imstability of 2,2'-bipyridine molecules adsorbed on Au(111) in terms of electronic structure calculations}, volume={29}, number={2}, journal={Bulletin of the Korean Chemical Society}, author={Suh, Y. and Park, S. S. and Kang, J. and Hwang, Y. G. and Jung, D. and Kim, D. H. and Lee, K. H. and Whangbo, M. H.}, year={2008}, pages={438–444} }
 @article{koehler_whangbo_2008, title={Late transition metal anions acting as p-metal elements}, volume={10}, ISSN={["1293-2558"]}, DOI={10.1016/j.solidstatesciences.2007.12.001}, abstractNote={A brief review is given for those extended solids of transition metal compounds in which their transition metal atoms are best described as existing as anions. Analyses of the electronic structures of metal-rich fluorides and oxides containing octahedral metallo-complexes [MIn6−xSnx] (M = Fe, Ni, Ru, Os, Ir and Pt) indicate that their transition metal atoms M are present as anions with the valence electron configuration (n + 1)s2nd10. In compounds RE2M2In (RE = rare earth element, M = Pt, Cu and Au), Ca5Au4, Ca3Hg2 and Ca5M3 (M = Cu, Au, Zn, Cd and Hg), the transition metal atoms exist as dimeric Zintl anions with the valence electron configuration (n + 1)s2nd10(n + 1)p1. Consequently, the frontier orbitals of these compounds are not described by the transition metal nd orbitals, but by the transition metal (n + 1)p orbitals. A similar situation is found for most 18-electron half-Heusler compounds (e.g., ScAuSn), for which the valence electron configuration of the transition metal is given by (n + 1)s2nd10(n + 1)p2.}, number={4}, journal={SOLID STATE SCIENCES}, author={Koehler, Juergen and Whangbo, Myung-Hwan}, year={2008}, month={Apr}, pages={444–449} }
 @article{chan_lee_dai_whangbo_ibers_2008, title={On the anisotropy of the magnetic properties of CsYbZnSe3}, volume={47}, ISSN={["1520-510X"]}, DOI={10.1021/ic701961f}, abstractNote={DC magnetic susceptibility measurements on CsYbZnSe 3 show a broad magnetic transition at approximately 10 K and pronounced differences between zero-field-cooled and field-cooled data that lead to experimental effective magnetic moments of 4.26(5) BM and 4.39(4) BM, respectively. Specific heat measurements confirm that there is neither long-range ordering nor a phase transition between 1.8 and 380 K. First-principles electronic structure calculations with and without inclusion of spin-orbit coupling effects show that the spins of CsYbZnSe 3 prefer to orient along [010] rather than along either [100] or [001] of this orthorhombic material and that the spin exchange between adjacent Yb3+ ions along [100] is substantially antiferromagnetic. The magnetic properties of CsYbZnSe 3 are best described by an Ising uniform antiferromagnetic chain model.}, number={5}, journal={INORGANIC CHEMISTRY}, author={Chan, George H. and Lee, Changhoon and Dai, Dad and Whangbo, Myung-Hwan and Ibers, James A.}, year={2008}, month={Mar}, pages={1687–1692} }
 @article{koo_whangbo_2008, title={On the correct spin lattice for the spin-gapped magnetic solid NH4CuPO4 center dot H2O}, volume={181}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2007.11.033}, abstractNote={NH4CuPO4·H2O is a spin-gapped compound that has been described in terms of an isolated antiferromagnetic spin dimer model. To explore the origin of this spin gap, we examined the spin exchange interactions of NH4CuPO4·H2O by performing qualitative spin dimer analysis based on extended Hückel tight binding calculations and also by carrying out quantitative mapping analysis based on first principles density functional theory electronic band structure calculations. Our study indicates that, to a first approximation, the magnetic properties of NH4CuPO4·H2O should be described by an antiferromagnetic and ferromagnetic alternating chain.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2008}, month={Feb}, pages={276–281} }
 @article{thiry_gaudon_payen_daro_letard_gorsse_deniard_rocquefelte_demourgues_whangbo_et al._2008, title={On the cyclability of the thermochromism in CuMoO4 and its tungsten derivatives CuMo1-xWxO4 (x < 0.12)}, volume={20}, ISSN={["1520-5002"]}, DOI={10.1021/cm703600g}, abstractNote={The cyclability of thermochromism in CuMoO4 and its solid solution CuMo1–xWxO4 (x < 0.12) was investigated by optical absorbance, differential scanning calorimetry, and magnetic susceptibility measurements. The high temperature form is found to progressively lose its ability to become the low temperature form with increasing the number of cooling/warming cycles.}, number={6}, journal={CHEMISTRY OF MATERIALS}, author={Thiry, Anne-Emmanuelle and Gaudon, Manuel and Payen, Christophe and Daro, Nathalie and Letard, Jean-Francois and Gorsse, Stephane and Deniard, Philippe and Rocquefelte, Xavier and Demourgues, Alain and Whangbo, Myung-Hwan and et al.}, year={2008}, month={Mar}, pages={2075–2077} }
 @article{yang_dai_huang_whangbo_2008, title={On the possibility of ferromagnetism in carbon-doped anatase TiO2}, volume={93}, number={13}, journal={Applied Physics Letters}, author={Yang, K. S. and Dai, Y. and Huang, B. B. and Whangbo, M. H.}, year={2008} }
 @article{xiang_wei_whangbo_2008, title={Origin of the structural and magnetic anomalies of the layered compound SrFeO2: A density functional investigation}, volume={100}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.100.167207}, abstractNote={The structural and magnetic anomaly of the layered compound ${\mathrm{SrFeO}}_{2}$ are examined by first-principles density functional calculations and Monte Carlo simulations. The down-spin Fe $3d$ electron occupies the ${d}_{{z}^{2}}$ level rather than the degenerate (${d}_{xz}$, ${d}_{yz}$) levels, which explains the absence of a Jahn-Teller instability, the easy $ab$-plane magnetic anisotropy, and the observed three-dimensional (0.5, 0.5, 0.5) antiferromagnetic order. Monte Carlo simulations show that the strong interlayer spin exchange is essential for the high N\'eel temperature.}, number={16}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Wei, Su-Huai and Whangbo, M. -H.}, year={2008}, month={Apr} }
 @article{xiang_wei_whangbo_da silva_2008, title={Spin-orbit coupling and ion displacements in multiferroic TbMnO(3)}, volume={101}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.101.037209}, abstractNote={The magnetic and ferroelectric (FE) properties of ${\mathrm{TbMnO}}_{3}$ are investigated on the basis of relativistic density functional theory calculations. We show that, due to spin-orbit coupling, the spin-spiral plane of ${\mathrm{TbMnO}}_{3}$ can be either the $bc$ or $ab$ plane, but not the $ac$ plane. As for the mechanism of FE polarization, our work reveals that the ``pure electronic'' model by Katsura, Nagaosa, and Balatsky is inadequate in predicting the absolute direction of FE polarization. Our work indicates that to determine the magnitude and the absolute direction of FE polarization in spin-spiral states, it is crucial to consider the displacements of the ions from their centrosymmetric positions.}, number={3}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Wei, Su-Huai and Whangbo, M. -H. and Da Silva, Juarez L. F.}, year={2008}, month={Jul} }
 @article{kabbour_janod_corraze_danot_lee_whangbo_cario_2008, title={Structure and magnetic properties of oxychalcogenides A(2)F(2)Fe(2)OQ(2) (A = sr, ba; Q = s, se) with Fe2O square planar layers representing an antiferromagnetic checkerboard spin lattice}, volume={130}, ISSN={["1520-5126"]}, DOI={10.1021/ja711139g}, abstractNote={The oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se), which contain Fe2O square planar layers of the anti-CuO2 type, were predicted using a modular assembly of layered secondary building units and subsequently synthesized. The physical properties of these compounds were characterized using magnetic susceptibility, electrical resistivity, specific heat, (57)Fe Mossbauer, and powder neutron diffraction measurements and also by estimating their exchange interactions on the basis of first-principles density functional theory electronic structure calculations. These compounds are magnetic semiconductors that undergo a long-range antiferromagnetic ordering below 83.6-106.2 K, and their magnetic properties are well-described by a two-dimensional Ising model. The dominant antiferromagnetic spin exchange interaction between S = 2 Fe(2+) ions occurs through corner-sharing Fe-O-Fe bridges. Moreover, the calculated spin exchange interactions show that the A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) compounds represent a rare example of a frustrated antiferromagnetic checkerboard lattice.}, number={26}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Kabbour, Houria and Janod, Etienne and Corraze, Benoit and Danot, Michel and Lee, Changhoon and Whangbo, Myung-Hwan and Cario, Laurent}, year={2008}, month={Jul}, pages={8261–8270} }
 @article{xiang_lee_whangbo_2007, title={Absence of a spiral magnetic order in Li2CuO2 containing one-dimensional CuO2 ribbon chains}, volume={76}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.76.220411}, abstractNote={On the basis of first-principles density functional theory electronic structure calculations as well as classical spin analysis, we explored why the magnetic oxide ${\mathrm{Li}}_{2}{\mathrm{CuO}}_{2}$, consisting of ${\mathrm{CuO}}_{2}$ ribbon chains made up of edge-sharing ${\mathrm{CuO}}_{4}$ squares, does not exhibit a spiral-magnetic order. Our work shows that, due to the next-nearest-neighbor interchain interactions, the observed collinear magnetic structure becomes only slightly less stable than the spin-spiral ground state and many states become nearly degenerate in energy with the observed collinear structure. This suggests that the collinear magnetic structure of ${\mathrm{Li}}_{2}{\mathrm{CuO}}_{2}$ is a consequence of order by disorder induced by next-nearest-neighbor interchain interactions.}, number={22}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Lee, C. and Whangbo, M. -H.}, year={2007}, month={Dec} }
 @article{manson_lancaster_schlueter_blundell_brooks_pratt_nygren_koo_dai_whangbo_2007, title={Characterization of the crystal and magnetic structures of the mixed-anion coordination polymer Cu(HCO2)(NO3)(pyz) {pyz = pyrazine} by X-ray diffraction, ac magnetic susceptibility, dc magnetization, muon-spin relaxation, and spin dimer analysis}, volume={46}, ISSN={["1520-510X"]}, DOI={10.1021/ic061590q}, abstractNote={The mixed-anion coordination polymer Cu(HCO2)(NO3)(pyz) was synthesized, its crystal structure was determined by X-ray diffraction, and its magnetic structure was characterized by ac susceptibility, dc magnetization, muon-spin relaxation, and spin dimer analysis. The crystal structure consists of five-coordinate Cu2+ ions that are connected through syn−anti bridging μ-HCO2- and μ-pyz ligands to form a highly corrugated two-dimensional layered network. Bulk magnetic measurements show a broad maximum in χ(T) at 6.6 K. The HCO2- and pyz ligands mediate ferromagnetic and antiferromagnetic spin exchange interactions between adjacent Cu2+ ions with the spin exchange parameters J/kB = 8.17 and −5.4 K, respectively (H = −JΣSi·Sj). The muon-spin relaxation data show a transition to a long-range magnetic ordering below TN = 3.66(3) K. For T < TN, the M(H) and χ‘ac measurements provide evidence for a field-induced spin-flop transition at 15.2 kOe. That Cu(HCO2)(NO3)(pyz) undergoes a long-range magnetic ordering is an unexpected result because the one-dimensional Cu(NO3)2(pyz) and three-dimensional Cu(HCO2)2(pyz) compounds display linear chain antiferromagnetism with no long-range magnetic ordering down to 2 K.}, number={1}, journal={INORGANIC CHEMISTRY}, author={Manson, J. L. and Lancaster, T. and Schlueter, J. A. and Blundell, S. J. and Brooks, M. L. and Pratt, F. L. and Nygren, C. L. and Koo, H. -J. and Dai, D. and Whangbo, M. -H.}, year={2007}, month={Jan}, pages={213–220} }
 @article{xiang_whangbo_2007, title={Charge order and the origin of giant magnetocapacitance in LuFe2O4}, volume={98}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.98.246403}, abstractNote={The nature of the charge order in the charge frustrated compound LuFe$_2$O$_4$ and its effect on magnetocapacitance were examined on the basis of first-principles electronic structure calculations and Monte Carlo simulations of electrostatic energy. Our work shows that two different types of charge order of almost equal stability (i.e., $\sqrt{3}\times \sqrt{3}$ and chain types) occur in the W-layers of LuFe$_2$O$_4$, and that the ground state of LuFe$_2$O$_4$ has a ferrielectric arrangement of the W-layers with $\sqrt{3}\times \sqrt{3}$ charge order. The giant magnetocapacitance effect of LuFe$_2$O$_4$ at room temperature is accounted for in terms of charge fluctuations arising from the interconversion between the two types of charge order, that becomes hindered by an applied magnetic field.}, number={24}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Whangbo, M.-H.}, year={2007}, month={Jun} }
 @article{angst_khalifah_hermann_xiang_whangbo_varadarajan_brill_sales_mandrus_2007, title={Charge order superstructure with integer iron valence in Fe2OBO3}, volume={99}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.99.086403}, abstractNote={Solution-grown single crystals of ${\mathrm{Fe}}_{2}{\mathrm{OBO}}_{3}$ were characterized by specific heat, M\"ossbauer spectroscopy, and x-ray diffraction. A peak in the specific heat at 340 K indicates the onset of charge order. Evidence for a doubling of the unit cell at low temperature is presented. Combining structural refinement of diffraction data and M\"ossbauer spectra, domains with diagonal charge order are established. Bond-valence-sum analysis indicates integer valence states of the Fe ions in the charge ordered phase, suggesting ${\mathrm{Fe}}_{2}{\mathrm{OBO}}_{3}$ is the clearest example of ionic charge order so far.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Angst, M. and Khalifah, P. and Hermann, R. P. and Xiang, H. J. and Whangbo, M.-H. and Varadarajan, V. and Brill, J. W. and Sales, B. C. and Mandrus, D.}, year={2007}, month={Aug} }
 @article{rocquefelte_jobic_whangbo_2007, title={Concept of optical channel as a guide for tuning the optical properties of insulating materials}, volume={9}, ISSN={["1873-3085"]}, DOI={10.1016/j.solidstatesciences.2007.04.008}, abstractNote={The utility of the concept of optical channel in understanding the optical properties of insulating materials was briefly reviewed by considering how the indices of refraction n of the seven TiO2 allotropes, TiOF2, TiF4 and the binary compounds MQ (M = Zn, Cd; Q = O, S, Se, Te) are related to their total absorption power per formula unit I(ɛ2) × V and their formula unit volume V. Important factors governing the optical properties of insulating materials are discussed.}, number={7}, journal={SOLID STATE SCIENCES}, author={Rocquefelte, Xavier and Jobic, Stephane and Whangbo, Myung-Hwan}, year={2007}, month={Jul}, pages={600–603} }
 @article{xiang_whangbo_2007, title={Cooperative effect of electron correlation and spin-orbit coupling on the electronic and magnetic properties of Ba2NaOsO6}, volume={75}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.75.052407}, abstractNote={The electronic and magnetic properties of the cubic double perovskite Ba2NaOsO6 were examined by performing first-principles density functional theory calculations and analyzing spin-orbit coupled states of an Os7+ (d1) ion at an octahedral crystal field. The insulating behavior of Ba2NaOsO6 was shown to originate from a cooperative effect of electron correlation and spin-orbit coupling. This cooperative effect is responsible not only for the absence of orbital ordering in Ba2 NaOsO6 but also for a small magnetic moment and a weak magnetic anisotropy in Ba2NaOsO6.}, number={5}, journal={PHYSICAL REVIEW B}, author={Xiang, H. J. and Whangbo, M. -H.}, year={2007}, month={Feb} }
 @article{xiang_whangbo_2007, title={Density-functional characterization of the multiferroicity in spin spiral chain cuprates}, volume={99}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.99.257203}, abstractNote={The ferroelectricity of the spiral magnets LiCu2O2 and LiCuVO4 was examined by calculating the electric polarizations of their spin spiral states on the basis of density functional theory with spin-orbit coupling. Our work unambiguously reveals that spin-orbit coupling is responsible for the ferroelectricity with the primary contribution from the spin-orbit coupling on the Cu sites, but the asymmetric density distribution responsible for the electric polarization occurs mainly around the O atoms. The electric polarization is calculated to be much greater for the ab- than for the bc-plane spin spiral. The observed spin-spiral plane is found to be consistent with the observed direction of the electric polarization for LiCuVO4, but inconsistent for LiCu2O2.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Xiang, H. J. and Whangbo, M. -H.}, year={2007}, month={Dec} }
 @article{matar_subramanian_villesuzanne_eyert_whangbo_2007, title={First principles investigation of the electronic structure of La2MnNiO6: An insulating ferromagnet}, volume={308}, ISSN={["0304-8853"]}, DOI={10.1016/j.jmmm.2006.05.029}, abstractNote={Using first principles density functional theory (DFT) calculations based on the full-potential linearized augmented plane wave method (LAPW), we investigated the electronic and magnetic structures for the ferromagnetic and antiferromagnetic states of La2MnNiO6 and analyzed the site-projected density of states and electronic dispersion curves. Our calculations show that the ground state of La2MnNiO6 is ferromagnetic insulating with the magnetization in agreement with Hund's first rule and experimental findings.}, number={1}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Matar, S. F. and Subramanian, M. A. and Villesuzanne, A. and Eyert, V. and Whangbo, M. -H.}, year={2007}, month={Jan}, pages={116–119} }
 @article{matar_eyert_villesuzanne_whangbo_2007, title={First-principles study of the electronic and magnetic structures of the tetragonal and orthorhombic phases of Ca3Mn2O7}, volume={76}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.76.054403}, abstractNote={On the basis of density functional theory electronic band structure calculations using the augmented spherical wave method, the electronic and magnetic properties of the orthorhombic and tetragonal phases of ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ were investigated and the spin exchange interactions of the orthorhombic phase were analyzed. Our calculations show that the magnetic insulating states are more stable than the nonmagnetic metallic state for both polymorphs of ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$, the orthorhombic phase is more stable than the tetragonal phase, and the ground state of the orthorhombic phase is antiferromagnetic. The total energies calculated for the three spin states of the orthorhombic phase of ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ led to estimates of the spin exchange interactions ${J}_{\mathit{nn}}=\ensuremath{-}3.36\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ and ${J}_{\mathit{nnn}}=\ensuremath{-}0.06\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The accuracy of these estimates was tested by calculating the Curie-Weiss temperature within the mean-field approximation.}, number={5}, journal={PHYSICAL REVIEW B}, author={Matar, S. F. and Eyert, V. and Villesuzanne, A. and Whangbo, M.-H.}, year={2007}, month={Aug} }
 @article{angst_hermann_schweika_kim_khalifah_xiang_whangbo_kim_sales_mandrus_2007, title={Incommensurate charge order phase in Fe2OBO3 due to geometrical frustration}, volume={99}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.99.256402}, abstractNote={The temperature dependence of charge order in Fe2OBO3 was investigated by resistivity and differential scanning calorimetry measurements, Mössbauer spectroscopy, and synchrotron x-ray scattering, revealing an intermediate phase between room temperature and 340 K, characterized by coexisting mobile and immobile carriers, and by incommensurate superstructure modulations with temperature-dependent propagation vector (1/2, 0, tau). The incommensurate modulations arise from specific antiphase boundaries with low energy cost due to geometrical charge frustration.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Angst, M. and Hermann, R. P. and Schweika, W. and Kim, J. -W. and Khalifah, P. and Xiang, H. J. and Whangbo, M. -H. and Kim, D. -H. and Sales, B. C. and Mandrus, D.}, year={2007}, month={Dec} }
 @article{koehler_friedrich_lee_whangbo_2007, title={IrIn7GeO8=[IrIn6](GeO4)(InO4) and compounds of the solid solution series [IrIn6](Ge1+xIn1-4x/O-3(8)) (0 <= x <= 0.75): First oxides containing [IrIn6] octahedra}, volume={633}, ISSN={["1521-3749"]}, DOI={10.1002/zaac.200700126}, abstractNote={Abstract IrIn 7 GeO 8 = [IrIn 6 ](GeO 4 )(InO 4 ) and Compounds of the Solid Solution Series [IrIn 6 ](Ge 1+x In 1−4x/3 O 8 ) (0 ≤ x ≤ 0.75): First Oxides containing [IrIn 6 ] Octahedra The low valent indiumoxides IrIn 7 GeO 8 = [IrIn 6 ](GeO 4 )(InO 4 ) and [IrIn 6 ](Ge 1+x In 1−4x/3 O 8 ) (0 x ≤ 0.75) are formed by heating intimate mixtures of Ir, In, In 2 O 3 and GeO 2 in corundum crucibles under an atmosphere of argon (1420 K, 70 h). The compounds are black and semiconducting. X‐ray powder diffraction patterns can be indexed on the basis of a face centered cubic unit cell with lattice parameters ranging from a = 1012.3(1) pm (x = 0) to a = 1007.3(1) pm (x = 0.75). Characteristic building units in [IrIn 6 ](Ge 1+x In 1−4x/3 O 8 ) are isolated [IrIn 6 ] 9+ octahedra with short Ir‐In distances of 253.5 pm, which are linked via [GeO 4 ] 4− and [InO 4 ] 5− tetrahedra to a three dimensional framework. Starting from IrIn 7 GeO 8 = [IrIn 6 ](GeO 4 )(InO 4 ), the isoelectronic substitution of 4 In 3+ ions by 3 Ge 4+ ions and one Ge‐vacancy leads to the formation of a solid solution series [IrIn 6 ](GeO 4 ) 1+x (O 4 ) x/3 (InO 4 ) 1−4x/3 , which shows a slight decrease in the cubic lattice parameter with increasing x. According to Rietveld refinements the structure of [IrIn 6 ](GeO 4 )(InO 4 ) exhibits a statistical distribution of the tetrahedrally coordinated Ge and In atoms ( , R(prof.) = 4.4 %, R(int.) = 2.5 %). The crystal and electronic structures of [IrIn 6 ](GeO 4 )(InO 4 ) are discussed on the basis of first principles electronic structure calculations.}, number={9}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Koehler, Juergen and Friedrich, Holger A. and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2007}, pages={1464–1471} }
 @article{belik_koo_whangbo_tsujii_naumov_takayama-muromachi_2007, title={Magnetic properties of synthetic libethenite Cu2PO4OH: a new spin-gap system}, volume={46}, ISSN={["0020-1669"]}, DOI={10.1021/ic7008418}, abstractNote={Synthetic mineral libethenite Cu2PO4OH was prepared by the hydrothermal method, and its structure at 200 K was refined by single-crystal X-ray diffraction. The structure of Cu2PO4OH is built up from Cu22O6(OH)2 dimers of edge-sharing Cu2O4(OH) trigonal bipyramids and [Cu12O6(OH)2]∝ chains of edge-sharing Cu1O4(OH)2 octahedra. Magnetic properties of Cu2PO4OH were investigated by magnetic susceptibility, magnetization, and specific heat measurements. Cu2PO4OH is a spin-gap system with a spin gap of about 139 K. It was shown by spin dimer analysis that, to a first approximation, the magnetic structure of Cu2PO4OH is described by an isolated square-spin cluster model defined by the Cu1−O−Cu2 superexchange J with Cu1···Cu2 = 3.429 Å. The fitting analysis of the magnetic susceptibility data with a square-spin cluster model results in J/kB = 138 K. Specific heat data show that Cu2PO4OH does not undergo a long-range magnetic ordering down to 1.8 K. We also report vibrational properties studied with Raman spectroscopy and the thermal stability of Cu2PO4OH.}, number={21}, journal={INORGANIC CHEMISTRY}, author={Belik, Alexei A. and Koo, Hyun-Joo and Whangbo, Myung-Hwan and Tsujii, Naohito and Naumov, Pance and Takayama-Muromachi, Eiji}, year={2007}, month={Oct}, pages={8684–8689} }
 @article{lee_whangbo_villesuzanne_2007, title={On the electronic structure required for the uniaxial magnetic properties of the magnetic metal SrCo6O11}, volume={19}, ISSN={["1520-5002"]}, DOI={10.1021/cm0706191}, abstractNote={On the basis of electronic structure analysis, it is shown that the total moment of SrCo6O11 per formula unit should be close to 6 μB, rather than 4 μB reported experimentally, to explain its uniaxial magnetic properties.}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changhoon and Whangbo, Myung-Hwan and Villesuzanne, Antoine}, year={2007}, month={May}, pages={2712–2714} }
 @article{koehler_deng_lee_whangbo_2007, title={On the origin of a band gap in compounds of diamond-like structures}, volume={46}, ISSN={["0020-1669"]}, DOI={10.1021/ic062256x}, abstractNote={Electronic structure calculations were performed to examine the origin of a band gap present in most 18-electron half-Heusler compounds and its absence in NaTl. In these compounds of diamond-like structures, the presence or absence of a band gap is controlled by the sigma antibonding between the valence s orbitals, and the bonding characteristics of the late-main-group elements depend on the extent of their ns/np hybridization. Implications of these observations on the formal oxidation state and the covalent bonding of the transition-metal atoms in 18-electron half-Heusler and related compounds were discussed.}, number={6}, journal={INORGANIC CHEMISTRY}, author={Koehler, Jurgen and Deng, Shuiquan and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2007}, month={Mar}, pages={1957–1959} }
 @article{clabau_rocquefelte_jobic_deniard_whangbo_garcia_le mercier_2007, title={On the phosphorescence mechanism in SrAl2O4 : Eu2+ and its codoped derivatives}, volume={9}, ISSN={["1293-2558"]}, DOI={10.1016/j.solidstatesciences.2007.03.020}, abstractNote={The mechanism of phosphorescence in SrAl2O4:Eu,Dy material is discussed on the basis of a thermo-activated release of electrons trapped at oxygen vacancy sites. The depths and concentration of the electron traps are strongly affected by codoping with trivalent lanthanide cations Ln3+. This finding is rationalized by comparing the ionization potentials of the dopant cation Eu2+, the codopant cation Ln3+ and the substituted cation Sr2+. Such a use of ionization potentials provides a practical guide with which the variation of the phosphorescent decay time in the codoped derivatives of SrAl2O4:Eu is predicted.}, number={7}, journal={SOLID STATE SCIENCES}, author={Clabau, Ferderic and Rocquefelte, Xavier and Jobic, Stephane and Deniard, Philippe and Whangbo, Myung-Hwan and Garcia, Alain and Le Mercier, Thierry}, year={2007}, month={Jul}, pages={608–612} }
 @article{koo_lee_wilson-short_dai_whangbo_2007, title={On the relevance of an antiferromagnetic dimer model for the spin-gapped magnetic solids Cu(terpy)Mo2O7 and Cu(OH)(p-pyc)H2O}, volume={46}, ISSN={["1520-510X"]}, DOI={10.1021/ic061897p}, abstractNote={The magnetic solids Cu(terpy)Mo2O7 (terpy = terpyridine) and Cu(OH)(p-pyc)H2O (p-pyc = p-pyridinecarboxylate) have a spin gap and possess chains of Cu2+ ions in which two different Cu···Cu distances alternate. On the basis of their reported crystal structures, the spin-exchange interactions of these compounds were examined by performing spin dimer analysis to determine whether an antiferromagnetic dimer or an alternating antiferromagnetic chain model is appropriate for their magnetic properties. Our analysis shows that an antiferromagnetic dimer model is correct for both compounds because of the anisotropic overlap between the magnetic orbitals of their Cu2+ sites.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Lee, Changhoon and Wilson-Short, Gareth B. and Dai, Dadi and Whangbo, Myung-Hwan}, year={2007}, month={Apr}, pages={2498–2502} }
 @article{lee_dieckmann_lee_whangbo_2007, title={Predicting anisotropic electrical conductivities of a magnetic insulator on the basis of its magnetic properties}, volume={19}, ISSN={["1520-5002"]}, DOI={10.1021/cm071481p}, abstractNote={Our analysis of the spin exchange interactions and the anisotropic electrical conductivities of the orthosilicate, fayalite Fe2SiO4 indicates that the anisotropic electrical conductivities of a mag...}, number={18}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Kee Hag and Dieckmann, Ruediger and Lee, Changhoon and Whangbo, Myung-Hwan}, year={2007}, month={Sep}, pages={4393–4395} }
 @article{rocquefelte_clabau_paris_deniard_le mercier_jobic_whangbo_2007, title={Resolving the aluminum ordering in aluminosilicates by a combined experimental/theoretical study of Al-27 electric field gradients}, volume={46}, ISSN={["0020-1669"]}, DOI={10.1021/ic7004166}, abstractNote={The discrimination between atomic species in light-element materials is a challenging question. An archetypal example is the resolution of the Al/Si ordering in aluminosilicates. Only an average long-range order can be deduced from powder X-ray or neutron diffraction, while magic-angle-spinning NMR provides an accurate picture of the short-range order. The long- and short-range orders thus obtained usually differ, hence raising the question of whether the difference between local and extended orders is intrinsic or caused by the difficulty of obtaining an accurate picture of the long-range order from diffraction techniques. In this communication we resolve this question for the monoclinic phases of BaAl2Si2O8 and SrAl2Si2O8 on the basis of 27Al NMR measurements and ab initio simulation of electric field gradient. Although the long- and short-range orders deduced from our XRD and NMR experiments differ, they become similar when the XRD atomic positions are optimized by ab initio electronic structure calculations.}, number={14}, journal={INORGANIC CHEMISTRY}, author={Rocquefelte, Xavier and Clabau, Frederic and Paris, Michael and Deniard, Philippe and Le Mercier, Thierry and Jobic, Stephane and Whangbo, Myung-Hwan}, year={2007}, month={Jul}, pages={5456–5458} }
 @article{koo_whangbo_2007, title={Spin dimer analysis of the magnetic structures of A(2)V(3)O(9) (A = Ba, Sr) and eta-Na9V14O35: Importance of the V4+-O center dot center dot center dot O-V4+ super- superexchange interactions mediated by the O-V5+-O bridges}, volume={9}, ISSN={["1293-2558"]}, DOI={10.1016/j.solidstatesciences.2007.06.013}, abstractNote={Abstract Spin dimer analysis was carried out for the magnetic oxides of V4+ (d1) ions, A2V3O9 (A = Ba, Sr) and η-Na9V14O35, to account for their magnetic structures. After identifying the V(Oeq)4 square planes containing the magnetic orbitals of the V4+ (d1) ions, we analyzed the relative strengths of the various V–Oeq–V and V–Oeq⋯Oeq–V spin exchange interactions. The V–Oeq⋯Oeq–V spin exchange interactions mediated by Oeq–V5+–Oeq bridges are found to be crucial in determining the magnetic structures of A2V3O9 (A = Ba, Sr) and η-Na9V14O35. Our analysis suggests that η-Na9V14O35 should have two different spin gaps.}, number={9}, journal={SOLID STATE SCIENCES}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2007}, month={Sep}, pages={824–832} }
 @article{ben yahia_gaudin_lee_whangbo_darriett_2007, title={Structural and magnetic properties of a new type of ordered oxygen-deficient perovskite, KMnVO4}, volume={19}, ISSN={["1520-5002"]}, DOI={10.1021/cm070452b}, abstractNote={A new ternary vanadate KMnVO4 was prepared by a solid-state reaction and was shown to be a new type of ordered oxygen-deficient perovskite ABO3 - δ with δ = 1/3. Its formula can be rewritten as (K2,Mn)[Mn,V2]O8□1. An ordered distribution of potassium and manganese atoms in the A site and of vanadium and manganese atoms in the B site is observed. The manganese atoms are in distorted octahedral and tetrahedral sites, whereas all of the vanadium atoms form VO43- tetrahedra. This oxide contains four different types of high-spin Mn2+ ions in equal number. Magnetic susceptibility and specific heat measurements as well as spin dimer analysis show that substantial antiferromagnetic spin-exchange interactions occur primarily among three of the four different types of Mn2+ ions, and the fourth Mn2+ ion remains paramagnetic down to 2 K.}, number={23}, journal={CHEMISTRY OF MATERIALS}, author={Ben Yahia, H. and Gaudin, E. and Lee, C. and Whangbo, M. -H. and Darriett, J.}, year={2007}, month={Nov}, pages={5563–5569} }
 @article{lee_whangbo_koehler_2007, title={Stuffed graphite-like vs. stuffed diamond-like structures of the 18 valence electron compounds REAuSn (RE = sc, y, la-nd, sm, gd-lu)}, volume={633}, ISSN={["0044-2313"]}, DOI={10.1002/zaac.200700317}, abstractNote={18-electron compounds REML (RE = rare earth metal; M = Cu, Ag, Au; L = Ge, Sn) can adopt either the stuffed graphite-like (P63mc) or the stuffed diamond-like () structure. To understand why one structure is favored over the other, we carried out density functional theory electronic structure calculations for a number of REAuSn compounds. The stuffed graphite-like and stuffed diamond-like structures of an 18-electron compound REAuSn are quite similar in their electronic structures with the Au atoms best described as existing as anions. The diamond-like REML becomes possible only when the RE3+ ion is small and the M-L bond is long.}, number={15}, journal={ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE}, author={Lee, Changhoon and Whangbo, Myung-Hwan and Koehler, Juergen}, year={2007}, pages={2631–2634} }
 @article{koo_whangbo_2007, title={Tight-binding electronic structure study of the beta '- and beta ''-phases of the organic conducting salts (BEDT-TTF)(2)(IBr2)(0.2)(BrICI)(0.1)(ICI2)(0.7)]}, volume={28}, number={2}, journal={Bulletin of the Korean Chemical Society}, author={Koo, H. J. and Whangbo, M. H.}, year={2007}, pages={241–245} }
 @article{ben yahia_gaudin_darriet_dai_whangbo_2006, title={Comparison of the crystal structures and magnetic properties of the low- and high-temperature forms of AgCuPO4: Crystal structure determination, magnetic susceptibility measurements, and spin dimer analysis}, volume={45}, ISSN={["1520-510X"]}, DOI={10.1021/ic060484l}, abstractNote={The crystal structure of the low-temperature form of AgCuPO4 (i.e., α-AgCuPO4) was determined by powder X-ray diffraction and was compared with that of the high-temperature form of AgCuPO4 (i.e., β-AgCuPO4). The magnetic properties of the two forms were examined by measuring their magnetic susceptibilities and evaluating the relative strengths of their spin-exchange interactions on the basis of spin-dimer analysis. Both forms of AgCuPO4 have layers of Cu2P2O8 alternating with silver-atom double layers; β-AgCuPO4 has two Cu2P2O8 layers per unit cell, while α-AgCuPO4 has one. The coordinate environment of each Cu2+ ion is close to being a distorted square pyramid in α-AgCuPO4, but it is close to being a distorted trigonal bipyramid in β-AgCuPO4. The magnetic susceptibilities of α- and β-AgCuPO4 are well simulated by an antiferromagnetic alternating-chain model, which leads to J/kB = −146.1 K and αJ/kB = −75.8 K for α-AgCuPO4, and J/kB = −82.6 K and αJ/kB = −31.7 K for β-AgCuPO4 (with the convention in which the spin-exchange parameter between two adjacent spin sites is written as 2J). The spin gaps, Δ/kB, obtained from these parameters are 93.7 K for α-AgCuPO4 and 62.3 K for β-AgCuPO4. The strongest spin exchange in both forms of AgCuPO4 comes from a super-superexchange path, and this interaction is stronger for α-AgCuPO4 than for β-AgCuPO4 by a factor of ∼2, in good agreement with the experiment. Our analysis supports the use of this model for β-AgCuPO4 and indicates that the spin lattice of α-AgCuPO4 would be better described by a two-dimensional net made up of weakly interacting alternating chains.}, number={14}, journal={INORGANIC CHEMISTRY}, author={Ben Yahia, Hamdi and Gaudin, Etienne and Darriet, Jacques and Dai, Dadi and Whangbo, Myung-Hwan}, year={2006}, month={Jul}, pages={5501–5509} }
 @article{dai_whangbo_koehler_hoch_villesuzanne_2006, title={Electronic structure analysis of the difference between Cs2AgF4 and Rb2MnF4 in their magnetic properties and single-crystal structure determination of Rb2MnF4}, volume={18}, ISSN={["1520-5002"]}, DOI={10.1021/cm060465+}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Dai, D. and Whangbo, M. -H. and Koehler, J. and Hoch, C. and Villesuzanne, A.}, year={2006}, month={Jul}, pages={3281–3286} }
 @article{clabau_rocquefelte_le mercier_deniard_jobic_whangbo_2006, title={Formulation of phosphorescence mechanisms in inorganic solids based on a new model of defect conglomeration}, volume={18}, ISSN={["1520-5002"]}, DOI={10.1021/cm052728q}, abstractNote={The phosphorescence mechanisms of various phosphors were explored by taking into consideration the presence of interactions between dopant cations and vacancies as well as the effect of co-dopant cations on these interactions. Our study indicates that the distribution of dopant and co-dopant cations around vacancies is not random, and luminescent properties are strongly influenced by this nonrandom distribution. To a first approximation, the ionization potentials of dopants, co-dopants, and host cations can be used to rationalize their tendencies for this nonrandom distribution. On the basis of our analysis, we explained the properties of known phosphorescent materials, examined several factors important for designing new improved phosphors, and discussed how point defects might affect phosphorescence as well as fluorescence.}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Clabau, F. and Rocquefelte, X. and Le Mercier, T. and Deniard, P. and Jobic, S. and Whangbo, M-H.}, year={2006}, month={Jul}, pages={3212–3220} }
 @article{koo_whangbo_2006, title={Importance of the O-M-O bridges (M = V5+, Mo6+) for the spin-exchange interactions in the magnetic oxides of Cu2+ ions bridged by MO4 tetrahedra: Spin-lattice models of Rb2Cu2(MoO4)(3), BaCu2V2O8, and KBa3Ca4Cu3V7O28}, volume={45}, ISSN={["1520-510X"]}, DOI={10.1021/ic060392w}, abstractNote={The spin-lattice models relevant for the magnetic oxides Rb2Cu2(MoO4)3, BaCu2V2O8, and KBa3Ca4Cu3V7O28 were determined by evaluating the relative strengths of the spin-exchange interactions between their Cu2+ ions on the basis of spin dimer analysis. Our study shows that the O-M-O bridges (M = V5+, Mo6+) between the magnetic ions Cu2+, provided by the MO4 tetrahedra, are crucial for the spin-exchange interactions and hence for deducing the spin-lattice models needed to interpret the magnetic properties of these oxides. The spin-lattice model of Rb2Cu2(MoO4)3 is not a uniform chain but two interpenetrating spin ladders that interact weakly with geometric spin frustration. The spin-lattice model of BaCu2V2O8 is an alternating chain as expected, but the spin-exchange paths responsible for it differ from those expected. With respect to the strongest spin exchange of BaCu2V2O8, the spin exchange of KBa3Ca4Cu3V7O28 is only slightly weaker, but the strongest spin exchange of Rb2Cu2(MoO4)3 is much weaker. This difference in the spin-exchange strengths is caused by the difference in the bridging modes of the MO4 tetrahedra leading to these spin-exchange interactions.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Whangbo, Myung-Hwan}, year={2006}, month={May}, pages={4440–4447} }
 @article{whangbo_dai_lee_kremer_2006, title={On the conflicting pictures of magnetism for the frustrated triangular lattice antiferromagnet CuFeO2}, volume={18}, ISSN={["0897-4756"]}, DOI={10.1021/cm052634g}, abstractNote={The magnetic structures of the triangular lattice antiferromagnet CuFeO2 below 14 K are described by an Ising model despite the fact that its high-spin Fe3+ (d5) ions (S = 5/2, L = 0) cannot have a uniaxial magnetic moment. To resolve this puzzling picture of magnetism, we estimated the relative strengths of various spin-exchange interactions of CuFeO2 by performing a spin dimer analysis and then determined the relative stabilities of a number of ordered spin states of CuFeO2. Our calculations show that, in terms of a Heisenberg model, the noncollinear 120° spin arrangement predicted for a triangular lattice antiferromagnet is more stable than the collinear four-sublattice antiferromagnetic structure observed for CuFeO2 below 11 K. To find a probable cause for stabilizing the collinear spin alignment along the c axis below 14 K, we considered the defect ions Fe2+ and Cu2+ of the CuFeO2 lattice created by oxygen deficiency and oxygen excess, respectively. Our electronic structure analysis suggests that these defect ions generate uniaxial magnetic moments along the c axis and hence induce the surrounding Fe3+ ions to orient their moments along the c axis.}, number={5}, journal={CHEMISTRY OF MATERIALS}, author={Whangbo, MH and Dai, DD and Lee, KS and Kremer, RK}, year={2006}, month={Mar}, pages={1268–1274} }
 @article{whangbo_dai_2006, title={On the disorder of the Cl atom position in and its probable effect on the magnetic properties of (CuCl)LaNb2O7}, volume={45}, ISSN={["1520-510X"]}, DOI={10.1021/ic060104w}, abstractNote={The magnetic susceptibility of (CuCl)LaNb2O7 shows a spin gap despite the Cu(2+) ions in each CuClO2 layer forming a square lattice. To account for this observation, we explored implications of the disorder of the Cl-atom position in (CuCl)LaNb2O7 by considering possible ordered structures of CuCl4O2 octahedra in each CuClO2 layer, by identifying various spin exchange interactions of a CuClO2 layer and by estimating the relative strengths of these interactions in terms of spin dimer analysis. We then probed what kind of spin lattice is required for each CuClO2 layer to have a spin gap on the basis of the classical spin approximation. Our study suggests that the CuCl4O2 octahedra of each CuClO2 layer should be arranged such that the resulting spin lattice does not have uniform chains but ring clusters containing an even number of Cu atoms. Implications of this conclusion were discussed on the basis of the recently reported neutron scattering and magnetization studies of (CuCl)LaNb2O7.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Whangbo, Myung-Hwan and Dai, Dadi}, year={2006}, month={Aug}, pages={6227–6234} }
 @article{whangbo_dai_kremer_2006, title={On the origin of the metallic and anisotropic magnetic properties of NaxCoO2 (x approximate to 0.75)}, volume={45}, ISSN={["1520-510X"]}, DOI={10.1021/ic060691l}, abstractNote={Nonstoichiometric Na(x)CoO2 (0.5 < x < 1) consists of CoO2 layers made up of edge-sharing CoO6 octahedra and exhibits strongly anisotropic magnetic susceptibilities as well as metallic properties. A modified Curie-Weiss law was proposed for systems containing anisotropic magnetic ions to analyze the magnetic susceptibilities of Na(x)CoO2 (x approximately 0.75), and implications of this analysis were explored. Our study shows that the low-spin Co4+ (S = 1/2) ions of Na(x)CoO2 generated by the Na vacancies cause the anisotropic magnetic properties of Na(x)CoO2 and suggests that the six nearest-neighbor Co3+ ions of each Co4+ ion adopt the intermediate-spin electron configuration, thereby behaving magnetically like low-spin Co4+ ions. The Weiss temperature of Na(x)CoO2 is more negative along the direction of the lower g factor (i.e., theta|| < theta(perpendicular) < 0 and g|| < g(perpendicular)). The occurrence of intermediate-spin Co3+ ions surrounding each Co4+ ion accounts for the apparently puzzling magnetic properties of Na(x)CoO2 (x approximately 0.75), i.e., the large negative Weiss temperature, the three-dimensional antiferromagnetic ordering below approximately 22 K, and the metallic properties. The picture of the magnetic structure derived from neutron scattering studies below approximately 22 K is in apparent conflict with that deduced from magnetic susceptibility measurements between approximately 50 and 300 K. These conflicting pictures are resolved by noting that the spin exchange between Co3+ ions is more strongly antiferromagnetic than that between Co4+ and Co3+ ions.}, number={15}, journal={INORGANIC CHEMISTRY}, author={Whangbo, M. -H. and Dai, D. and Kremer, R. K.}, year={2006}, month={Jul}, pages={5989–5995} }
 @article{rocquefelte_jobic_whangbo_2006, title={On the volume-dependence of the index of refraction from the viewpoint of the complex dielectric function and the Kramers-Kronig relation}, volume={110}, ISSN={["1520-6106"]}, DOI={10.1021/jp055445u}, abstractNote={How indices of refraction n(ω) of insulating solids are affected by the volume dilution of an optical entity and the mixing of different, noninteracting simple solid components was examined on the basis of the dielectric function ε1(ω) + iε2(ω). For closely related insulating solids with an identical composition and the formula unit volume V, the relation [ε1(ω) − 1]V = constant was found by combining the relation ε2(ω)V = constant with the Kramers−Kronig relation. This relation becomes [n2(ω) − 1]V = constant for the index of refraction n(ω) determined for the incident light with energy less than the band gap (i.e., ℏω < Eg). For a narrow range of change in the formula unit volume, the latter relation is well approximated by a linear relation between n and 1/V.}, number={6}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Rocquefelte, X and Jobic, S and Whangbo, MH}, year={2006}, month={Feb}, pages={2511–2514} }
 @article{koo_lee_whangbo_2006, title={Spin dimer analysis of the magnetic structures of Ba3Cr2O8, Ba3Mn2O8, Na4FeO4, and Ba2CoO4 with a three-dimensional network of isolated MO4 (M = Cr, Mn, Fe, Co) tetrahedra}, volume={45}, ISSN={["1520-510X"]}, DOI={10.1021/ic061773c}, abstractNote={The spin exchange interactions of the magnetic oxides Ba3Cr2O8, Ba3Mn2O8, Na4FeO4, and Ba2CoO4 with a three-dimensional network of isolated MO4 (M = Cr, Mn, Fe, Co) tetrahedra were examined by performing spin dimer analysis on the basis of tight-binding electronic structure calculations. Although the shortest O...O distances between adjacent MO4 tetrahedra are longer than the van der Waals distance, our analysis shows that the super-superexchange interactions between adjacent MO4 tetrahedra are substantial and determine the magnetic structures of these oxides. In agreement with experiment, our analysis predicts a weakly interacting isolated AFM dimer model for both Ba3Cr2O8 and Ba3Mn2O8, the (0.0, 0.5, 0.0) magnetic superstructure for Na4FeO4, the (0.5, 0.0, 0.5) magnetic superstructure for Ba2CoO4, and the presence of magnetic frustration in Ba2CoO4. The comparison of the intra- and interdimer spin exchange interactions of Ba3Cr2O8 and Ba3Mn2O8 indicates that orbital ordering should be present in Ba3Cr2O8.}, number={26}, journal={INORGANIC CHEMISTRY}, author={Koo, Hyun-Joo and Lee, Kwang-Soon and Whangbo, Myung-Hwan}, year={2006}, month={Dec}, pages={10743–10749} }
 @article{deisenhofer_eremina_pimenov_gavrilova_berger_johnsson_lemmens_nidda_loidl_lee_et al._2006, title={Structural and magnetic dimers in the spin-gapped system CuTe2O5}, volume={74}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.74.174421}, abstractNote={We investigated the magnetic properties of the system CuTe2O5 by susceptibility and electron spin resonance measurements. The anisotropy of the effective g-factors and the ESR linewidth indicates that the anticipated structural dimer does not correspond to the singlet-forming magnetic dimer. Moreover, the spin susceptibility of CuTe2O5 can only be described by taking into account interdimer interactions of the same order of magnitude than the intradimer coupling. Analyzing the exchange couplings in the system we identify the strongest magnetic coupling between two Cu ions to be mediated by super-super exchange interaction via a bridging Te ligand, while the superexchange coupling between the Cu ions of the structural dimer only results in the second strongest coupling.}, number={17}, journal={PHYSICAL REVIEW B}, author={Deisenhofer, J. and Eremina, R. M. and Pimenov, A. and Gavrilova, T. and Berger, H. and Johnsson, M. and Lemmens, P. and Nidda, H. -A. Krug and Loidl, A. and Lee, K. -S. and et al.}, year={2006}, month={Nov} }
 @article{whangbo_subramanian_2006, title={Structural model of planar defects in CaCu3Ti4O12 exhibiting a giant dielectric constant}, volume={18}, ISSN={["0897-4756"]}, DOI={10.1021/cm060323f}, abstractNote={It is known that the unusually large dielectric constant in single crystals of CaCu3Ti4O12 (CCTO) requires the existence of barrier layers in the form of twin boundaries or planar defects within the crystals, and even the high dielectric constant of ceramic CCTO samples requires one to consider domain boundaries within the crystallites. As a probable origin of such domain boundaries, we proposed a structural model of plane defect that can result from a twinning parallel to the (100), (010), and (001) planes and examined its local electronic structures. This plane defect model provides a plausible microscopic explanation for the origin of gigantic dielectric constants in CCTO.}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Whangbo, MH and Subramanian, MA}, year={2006}, month={Jul}, pages={3257–3260} }
 @article{wang_hung_hwu_koo_whangbo_2006, title={Synthesis, structure, and properties of a new family of mixed-framework chalcohalide semiconductors: CdSbS2X (X = Cl, Br), CdBiS2X (X = Cl, Br), and CdBiSe2X (X = Br, I)}, volume={18}, ISSN={["1520-5002"]}, DOI={10.1021/cm0522230}, abstractNote={A new family of quaternary mixed-framework chalcohalide semiconductors has been synthesized by conventional solid-state reactions in an intermediate temperature region of 400−430 °C. These include CdSbS2Cl (1), CdSbS2Br (2), CdBiS2Cl (3), CdBiS2Br (4), CdBiSe2Br (5), and CdBiSe2I (6). Single-crystal structure analyses of this compound series reveal two types of crystal structures depending upon the combination of chalcohalide anions, and they crystallize in an orthorhombic Pnma (type I) and monoclinic C2/m (type II) space group. Type I is adopted by two sulfochlorides, 1 and 3, and one selenobromide, 5. Type II is adopted by two sulfobromides, 2 and 4, and one selenoiodide, 6. Both structure types have slabs built of corner and edge shared Cd-centered CdQ6-xXx (Q = S, Se; X = Cl, Br, I; x = 0, 2, 4) octahedra that resemble the (110) plane of a distorted NaCl-type structure. In the type I structure, this slab contains only CdQ4X2 octahedra, while type II shows alternating CdQ6 and CdQ2X4 octahedra. In both structure types, each M3+ (M = Sb, Bi) cation of CdMQ2X forms a distorted square pyramid, MQ5, as found in M2Q3. The MQ5 unit is weakly coordinated to three X atoms to form a distorted bicapped trigonal prism, MQ5X3. In forming the extended network structure, the CdQ6-xXx and MQ5X3 units are solely linked through chalcogenide anions. The Fourier transform infrared spectroscopy studies suggest that these chalcohalides are transparent in the mid-IR region (1400−4000 cm-1). The UV−vis spectroscopy results in a band gap ranging from 1.3 to 2.2 eV, showing a red shift with respect to the corresponding binary chalcogenides CdQ. The results of tight-binding electronic band structure calculations suggest that the origin of this red shift is due to the lone-pair effects from Sb and Bi.}, number={5}, journal={CHEMISTRY OF MATERIALS}, author={Wang, L and Hung, YC and Hwu, SJ and Koo, HJ and Whangbo, MH}, year={2006}, month={Mar}, pages={1219–1225} }
 @article{whangbo_lee_koehler_2006, title={Transition-metal anions in solids and their implications on bonding}, volume={45}, ISSN={["1433-7851"]}, DOI={10.1002/anie.200602712}, abstractNote={A negative disposition: Electronic-band-structure calculations reveal that in La2M2In (M=Pt, Cu) the transition-metal atoms can be regarded as anions with fully occupied nd orbitals and bonding characters similar to that of the Ge3− ions in La2Ge2In. The orbital sequence in La2M2In is (n+1)s<nd<(n+1)p, as a result of the low oxidation states of the transition metals (see graph).}, number={44}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Whangbo, Myung-Hwan and Lee, Changhoon and Koehler, Juergen}, year={2006}, pages={7465–7469} }
 @article{manson_conner_schlueter_lancaster_blundell_brooks_pratt_papageorgiou_bianchi_wosnitza_et al._2006, title={[Cu(HF2)(pyz)(2)]BF4 (pyz=pyrazine): long-range magnetic ordering in a pseudo-cubic coordination polymer comprised of bridging HF2- and pyrazine ligands}, number={47}, journal={Chemical Communications (Cambridge, England)}, author={Manson, J. L. and Conner, M. M. and Schlueter, J. A. and Lancaster, T. and Blundell, S. J. and Brooks, M. L. and Pratt, F. L. and Papageorgiou, T. and Bianchi, A. D. and Wosnitza, J. and et al.}, year={2006}, pages={4894–4896} }
 @article{dai_whangbo_ugrinov_sevov_wang_li_villesuzanne_alekseyev_liebermann_buenker_2005, title={Analysis of the effect of spin-orbit coupling on the electronic structure and excitation spectrum of the Bi-2(2-) anion in (K-crypt)(2)Bi-2 on the basis of relativistic electronic structure calculations}, volume={109}, ISSN={["1089-5639"]}, DOI={10.1021/jp044675q}, abstractNote={The Bi2(2-) anions that have been characterized in (K-crypt)2Bi2 are isoelectronic with O2 but are diamagnetic and EPR-silent, unlike O2. The UV-vis spectrum measured for (K-crypt)2Bi2 shows two broad absorption peaks located at 2.05 and 2.85 eV, but no absorption at lower energies down to 0.62 eV. To account for these observations, the electronic structures of the isoelectronic diatomic dianions Q2(2-) (Q = N, P, As, Sb, Bi) were compared on the basis of relativistic density functional theory calculations, and the electronic excitations of Bi2(2-) were analyzed on the basis of relativistic configuration interaction calculations. The extent of spin-orbit coupling, brought about by the relativistic effect, increases steadily in the order N < P < As < Sb < Bi such that the "closed-shell" state is more stable than the "open-shell" state for Bi2(2-), while the opposite is the case for N2(2-), P2(2-), As2(2-), and Sb2(2-). The nature of the electronic excitations of Bi2(2-) was assigned and discussed from the viewpoint of molecular orbitals in the absence of spin-orbit coupling.}, number={8}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Dai, D and Whangbo, MH and Ugrinov, A and Sevov, SC and Wang, F and Li, LM and Villesuzanne, A and Alekseyev, AB and Liebermann, HP and Buenker, RJ}, year={2005}, month={Mar}, pages={1675–1683} }
 @article{rocquefelte_goubin_montardi_viadere_demourgues_tressaud_whangbo_jobic_2005, title={Analysis of the refractive indices of TiO2, TiOF2, and TiF4: Concept of optical channel as a guide to understand and design optical materials}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic048259w}, abstractNote={In an effort to gain insight into how optical properties of insulating materials are affected by a change in chemical composition, we investigated the dielectric functions of titanium dioxide, TiO(2), and its fluorine-substituted phases, TiOF(2) and TiF(4), by electron energy loss spectroscopy measurements and density functional theory electronic band structure calculations. The refractive indices of these compounds are found to be inversely proportional to their cell volumes per formula unit. This observation was explained by employing the concept of optical channels. Our study indicates that the light-scattering properties of insulating compounds can be controlled by modifying their cell volumes.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Rocquefelte, X and Goubin, F and Montardi, Y and Viadere, N and Demourgues, A and Tressaud, A and Whangbo, MH and Jobic, S}, year={2005}, month={May}, pages={3589–3593} }
 @article{dal_whangbo_koo_rocquefelte_jobic_villesuzanne_2005, title={Analysis of the spin exchange interactions and the ordered magnetic structures of lithium transition metal phosphates LiMPO4 (M = Mn, Fe, Co, Ni) with the olivine structure}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic048431w}, abstractNote={The olivine-type compounds LiMPO4 (M = Mn, Fe, Co, Ni) consist of MO4 layers made up of corner-sharing MO6 octahedra of high-spin M2+ ions. To gain insight into the magnetic properties of these phosphates, their spin exchange interactions were estimated by spin dimer analysis using tight binding calculations and by electronic band structure analysis using first principles density functional theory calculations. Three spin exchange interactions were found to be important for LiMPO4, namely, the intralayer superexchange J1, the intralayer super-superexchange Jb along the b-direction, and the interlayer super-superexchange J2 along the b-direction. The magnetic ground state of LiMPO4 was determined in terms of these spin exchange interactions by calculating the total spin exchange interaction energy under the classical spin approximation. In the spin lattice of LiMPO4, the two-dimensional antiferromagnetic planes defined by the spin exchange J1 are antiferromagnetically coupled by the spin exchange J2, in agreement with available experimental data.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Dal, D and Whangbo, MH and Koo, HJ and Rocquefelte, X and Jobic, S and Villesuzanne, A}, year={2005}, month={Apr}, pages={2407–2413} }
 @article{dai_whangbo_2005, title={Analysis of the uniaxial magnetic properties of high-spin d(6) ions at trigonal prism and linear two-coordinate sites: Uniaxial magnetic properties of Ca3Co2O6 and Fe[C(SiMe3)(3)](2)}, volume={44}, ISSN={["0020-1669"]}, DOI={10.1021/ic050185g}, abstractNote={It was shown that high-spin d6 ions at trigonal prism and linear two coordinate sites have uniaxial magnetic properties by calculating their low-lying eigenstates under the influence of crystal field and spin−orbit coupling and then determining their g-factors for the parallel and perpendicular directions. On the basis of our theoretical findings, we interpreted the uniaxial magnetic properties of Ca3Co2O6 with high-spin Co3+ (d6) ions at the trigonal prism sites and those of Fe[C(SiMe3)3]2 with high-spin Fe2+ (d6) ions at linear two-coordinate sites, and discussed why compounds with high-spin d6 ions at octahedral sites cannot have uniaxial magnetic properties.}, number={12}, journal={INORGANIC CHEMISTRY}, author={Dai, DD and Whangbo, MH}, year={2005}, month={Jun}, pages={4407–4414} }
 @article{kohler_chang_whangbo_2005, title={Bonding and oxidation state of a transition metal atom encapsulated in an isolated octahedral cluster cation of main group elements: Synthesis, crystal structure, and electronic structure of Pt2In14Ga3O8F15 containing highly positive 18-electron complex [PtIn6](10+) and low-valent in(+) ions}, volume={127}, ISSN={["1520-5126"]}, DOI={10.1021/ja044389s}, abstractNote={Colorless transparent single crystals and white polycrystalline powder samples of Pt2In14Ga3(O)8F15 were obtained by heating a mixture of stoichiometric amounts of Pt, In, InF3, and Ga2(O)3, in a Pt crucible under Ar at 600 degrees C. The new oxyfluoride crystallizes in a new structure type in the trigonal space group Rm (No. 166) with a = 709.0(6) pm, c = 4556.4(3) pm, and Z = 6 with characteristic building units of PtIn6 octahedra (Pt-In = 255-257 pm), GaF6 octahedra (Ga-F = 189 pm), and GaO(4) tetrahedra (Ga-O = 186-187 pm). This oxyfluoride consists of a highly positive 18-electron complex [PtIn6]10+ as well as low-valent In+ ions. Electronic band structure calculations for Pt2In14(Ga3)O(8)F15 and molecular orbital (MO) calculations for [PtIn6]10+ were carried out to analyze the electronic structure of [PtIn6]10+ and estimate the oxidation state of Pt. Our analysis indicates that the oxidation state of the Pt atom in [PtIn6]10+ is negative rather than positive. For other octahedral cluster cations of main group elements stuffed with a transition metal atom (e.g., [RuSn6]14+ and "[IrBi6]11+") as well, we showed that the oxidation state of the transition metal atom is most probably negative by studying their electronic structures.}, number={7}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Kohler, J and Chang, JH and Whangbo, MH}, year={2005}, month={Feb}, pages={2277–2284} }
 @article{woodward_backov_abboud_dai_koo_whangbo_meisel_talham_2005, title={Dramatic variation of magnetic exchange through double end-on azide bridges in a series of ladder-like copper(II) coordination polymers}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic049175q}, abstractNote={Three ladder-like coordination polymers, [Cu2(phprpy)2-μ-(N3)2(N3)2], 1; [Cu2(terpy)2-μ-(N3)4Cu2-μ-(N3)2(N3)2], 2; and[Cu2(terpy)2-μ-(N3)2(N3)2Cu3-μ-(N3)4(N3)2], 3, consisting of Cu2+ ions with double end-on azide bridges were synthesized, their crystal structures and magnetic properties were determined, and spin dimer analysis was performed to explain the signs and strengths of their strong spin exchange interactions [phprpy is 4-(3-phenylpropyl)pyridine and terpy is 2,2‘:6,2‘ ‘-terpyridine]. Although these compounds have ladder-like arrangements of Cu2+ ions, their magnetic structures are described as isolated dimers for 1 and 2 and as isolated trimers for 3. The predominant spin exchange paths in 1−3 have double end-on azide bridges linking adjacent Cu2+ ions, and the geometrical parameters of these bridging structures are similar. However, the spin dimer of 1 exhibits a strong ferromagnetic coupling; that of 2, a strong antiferromagnetic coupling; and that of 3, a weak ferromagnetic coupling. These findings are well explained by the present spin dimer analysis and show that the nature and geometry of the nonbridging ligands can have a strong influence on the sign and strength of the spin exchange interaction between Cu2+ ions connected by double end-on azide bridges.}, number={3}, journal={INORGANIC CHEMISTRY}, author={Woodward, JD and Backov, RV and Abboud, KA and Dai, D and Koo, HJ and Whangbo, MH and Meisel, MW and Talham, DR}, year={2005}, month={Feb}, pages={638–648} }
 @article{koo_dai_whangbo_2005, title={Importance of supersuperexchange interactions in determining the dimensionality of magnetic properties. Determination of strongly interacting spin exchange paths in A(2)CU(PO4)(2) (A = Ba, Sr), ACuP(2)O(7) (Ba, Ca, Sr, Pb), CaCuGe2O6, and Cu2UO2(PO4)(2) on the basis of qualitative spin dimer analysis}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic050159i}, abstractNote={The patterns of the Cu2+ ion arrangements in the magnetic oxides A2Cu(PO4)2 (A = Ba, Sr), ACuP2O7 (Ba, Ca, Sr, Pb), CaCuGe2O6, and Cu2UO2(PO4)2 are quite different from the patterns of the strongly interacting spin exchange paths deduced from their magnetic properties. This apparently puzzling observation was explained by evaluating the strengths of the Cu−O−Cu superexchange and Cu−O···O−Cu supersuperexchange interactions of these oxides on the basis of qualitative spin dimer analysis. Supersuperexchange interactions are found to be crucial in determining the dimensionality of magnetic properties of these magnetic oxides.}, number={12}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Dai, D and Whangbo, MH}, year={2005}, month={Jun}, pages={4359–4365} }
 @article{belik_azuma_matsuo_whangbo_koo_kikuchi_kaji_okubo_ohta_kindo_et al._2005, title={Investigation of the crystal structure and the structural and magnetic properties of SrCu2(PO4)(2)}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic051079h}, abstractNote={SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) Å, b = 15.36918(14) Å, and c = 10.37036(10) Å. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1···Cu2 = 3.256 Å. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1−O···O−Cu2 and Cu2−O···O−Cu2 super-superexchange paths with Cu1···Cu2 = 5.861 Å and Cu2···Cu2 = 5.251 Å, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1−Cu2−Cu2−Cu1 with −2J1/kB = 82.4 K for Cu1−Cu2 and −2J2/kB = 59 K for Cu2−Cu2. A spin gap deduced from this model (Δ/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Δ/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Belik, AA and Azuma, M and Matsuo, A and Whangbo, MH and Koo, HJ and Kikuchi, J and Kaji, T and Okubo, S and Ohta, H and Kindo, K and et al.}, year={2005}, month={Sep}, pages={6632–6640} }
 @article{lee_suh_lee_hwang_koo_whangbo_2005, title={Investigation of the scanning tunneling microscopy image, the stacking pattern, and the bias-voltage-dependent structural instability of 1,10 '-phenanthroline molecules adsorbed on Au(111) in terms of electronic structure calculations}, volume={109}, ISSN={["1520-5207"]}, DOI={10.1021/jp051248j}, abstractNote={A self-assembled monolayer of 1,10'-phenanthroline (phen) molecules on Au(111) was found to undergo a structural phase transition when the bias voltage is switched in scanning tunneling microscopy (STM) experiments (Phys. Rev. Lett. 1995, 75, 2376; Surf. Sci. 1997, 389, 19). The nature of two bright spots representing each phen molecule in the high-resolution STM images of phen molecules on Au(111) was identified by calculating the partial density plots for a monolayer of phen molecules adsorbed on Au(111) with tight-binding electronic structure calculations. The stacking pattern of chains of phen molecules on Au(111) was explained by studying the intermolecular interactions between phen molecules on the basis of first-principles electronic structure calculations for a phen dimer, (phen)(2). The structural instability of phen molecule arrangement caused by the bias-voltage switch was probed by estimating the adsorbate-surface interaction energy with the point-charge approximation for Au(111).}, number={32}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Lee, KH and Suh, Y and Lee, C and Hwang, YG and Koo, HJ and Whangbo, MH}, year={2005}, month={Aug}, pages={15322–15326} }
 @article{kim_seo_kremer_kohler_villesuzanne_whangbo_2005, title={Large negative magnetoresistance of the rare-earth transition-metal intermetallic compound PrMnSi2}, volume={17}, ISSN={["0897-4756"]}, DOI={10.1021/cm051669d}, abstractNote={The rare-earth intermetallic compound PrMnSi2 consists of two magnetic sublattices, i.e., layers of Mn atoms and layers of Pr atoms, which repeat in the (−Mn−Pr−Pr−)∞ sequence. Electrical resistivity measurements were carried out for PrMnSi2 between 2 and 350 K under various magnetic fields. PrMnSi2 is a metal with two metal-to-metal transitions at ∼20 and ∼50 K, and its resistivity vs temperature curves show a significant hysteresis in the absence and presence of an external magnetic field. The resistivity is reduced by an external magnetic field, and this negative magnetoresistance reaches up to 47% at 9 T around 17 K where PrMnSi2 is antiferromagnetic at zero field. The magnetoresistance vs temperature curves of PrMnSi2 reveal three peaks at fields up to ∼3 T, which correspond to the three magnetic phase transitions of PrMnSi2 observed from magnetic susceptibility and heat capacity measurements. The negative magnetoresistance and the resistivity hysteresis of PrMnSi2 were accounted for by considering how the scattering of the electrons at the Fermi level is reduced by an applied field.}, number={25}, journal={CHEMISTRY OF MATERIALS}, author={Kim, SH and Seo, DK and Kremer, RK and Kohler, M and Villesuzanne, A and Whangbo, MH}, year={2005}, month={Dec}, pages={6338–6341} }
 @article{clabau_rocquefelte_jobic_deniard_whangbo_garcia_le mercier_2005, title={Mechanism of phosphorescence appropriate for the long-lasting phosphors Eu2+-doped SrAl2O4 with codopants Dy3+ and B3+}, volume={17}, ISSN={["1520-5002"]}, DOI={10.1021/cm050763r}, abstractNote={The existing mechanisms proposed to explain the phosphorescence of SrAl2O4:Eu2+,Dy3+ and related phosphors were found to be inconsistent with a number of important experimental and theoretical observations. We formulated a new mechanism of phosphorescence on the basis of the facts that the d orbitals of Eu2+ are located near the conduction band bottom of SrAl2O4, that the Eu2+ concentration decreases during UV excitation, and that trace amounts of Eu3+ are always present in these phosphors. In our mechanism, some Eu2+ ions are oxidized to Eu3+ under UV, and the released electrons are trapped at the oxygen vacancy levels located in the vicinity of the photogenerated Eu3+ cations. The phosphorescence arises from the recombination of these trapped electrons around the photogenerated Eu3+ sites with emission at 520 nm. The codopant Dy3+ enhances the phosphorescence by increasing the number and the depth of electron traps, and the codopant B3+ enhances the phosphorescence by increasing the depth of electron traps. We also probed the origin of another emission at 450 nm of SrAl2O4:Eu2+ that occurs at low temperatures. Our analysis indicates that this emission is caused by a charge transfer from oxygen to Eu3+ cations and is associated with a hole trapping.}, number={15}, journal={CHEMISTRY OF MATERIALS}, author={Clabau, F and Rocquefelte, X and Jobic, S and Deniard, P and Whangbo, MH and Garcia, A and Le Mercier, T}, year={2005}, month={Jul}, pages={3904–3912} }
 @article{kim_seo_kremer_kohler_villesuzanne_whangbo_2005, title={Observation of unusual hysteretic magnetic properties of the rare earth intermetallic compound PrMnSi2: Magnetic susceptibility, magnetization, heat capacity, and electronic band structure studies}, volume={17}, ISSN={["0897-4756"]}, DOI={10.1021/cm050622p}, abstractNote={The magnetic properties of the rare earth intermetallic compound PrMnSi2 were characterized by carrying out magnetic susceptibility, magnetization, and heat capacity measurements and performing APW+lo/LDA+U electronic band structure calculations for several ordered spin states of PrMnSi2. The temperature dependence of the magnetic susceptibilities shows strong hysteresis at low magnetic fields and exhibits hysteresis under magnetic fields up to ∼5 T. The magnetizations present unusual hysteresis loops as a function of temperature. The magnetic susceptibility and heat capacity measurements reveal that PrMnSi2 undergoes three magnetic phase transitions, one below ∼50 K and two below ∼20 K. The probable causes for the observed anomalous magnetic properties were discussed on the basis of nearly degenerate ordered spin states found from electronic structure calculations.}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Kim, SH and Seo, DK and Kremer, RK and Kohler, J and Villesuzanne, A and Whangbo, MH}, year={2005}, month={Jul}, pages={3711–3716} }
 @article{villesuzanne_whangbo_subramanian_matar_2005, title={Spin dimer and electronic band structure analyses of the ferromagnetism versus antiferromagnetism in SeCuO3 and TeCuO3}, volume={17}, ISSN={["0897-4756"]}, DOI={10.1021/cm050885j}, abstractNote={On the basis of spin dimer analysis and density functional theory electronic band structure calculations, we examined why the magnetic ground state of SeCuO3 is ferromagnetic while that of its isostructural analogue TeCuO3 is antiferromagnetic and estimated their spin exchange parameters. The essential difference between the magnetic properties of these oxides arises from their Cu−O(1)−Cu superexchange, but not their Cu−O(2)−Cu superexchange. Spin exchange paths relevant for understanding magnetic properties are those that contain magnetic orbitals.}, number={17}, journal={CHEMISTRY OF MATERIALS}, author={Villesuzanne, A and Whangbo, MH and Subramanian, MA and Matar, SF}, year={2005}, month={Aug}, pages={4350–4355} }
 @article{whangbo_dai_koo_2005, title={Spin dimer, electronic band structure and classical spin analyses of spin exchange interactions and ordered magnetic structures of magnetic solids}, volume={7}, ISSN={["1873-3085"]}, DOI={10.1016/j.solidstatesciences.2005.02.009}, abstractNote={We reviewed briefly how spin dimer, electronic band structure and classical spin analyses are employed to describe spin exchange interactions and ordered magnetic structures of magnetic solids. It was shown that super-superexchange interactions are crucial in forming strongly interacting spin units of magnetic solids and hence in determining their magnetic properties, and that incommensurate magnetic superstructures are readily described by a Heisenberg spin Hamiltonian using the classical spin approximation. We probed the weak ferrimagnetism of monoclinic Fe2(SO4)3 in terms of spin dimer and mean-field-theory analyses to explain both the ordered magnetic structure and the sublattice magnetization. The classical spin and quantum mechanical descriptions of geometric spin frustration were compared to clarify their differences.}, number={7}, journal={SOLID STATE SCIENCES}, author={Whangbo, MH and Dai, D and Koo, HJ}, year={2005}, month={Jul}, pages={827–852} }
 @article{rocquefelte_whangbo_jobic_2005, title={Structural and electronic factors controlling the refractive indices of the chalcogenides ZnQ and CdQ (Q = O, S, Se, Te)}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic048352k}, abstractNote={On the basis of first-principles electronic band structure theory, we calculated the refractive indices of the zinc blende and wurtzite structures of the chalcogenides ZnQ and CdQ (Q = O, S, Se, Te) and analyzed their trends by calculating the total absorption power per unit formula. The calculated refractive indices are in good agreement with the available experimental data. The total absorption power per formula unit is found to allow one to distinguish the effect of the chromophore from that of the cell volume on the refractive indices of insulating inorganic compounds.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Rocquefelte, X and Whangbo, MH and Jobic, S}, year={2005}, month={May}, pages={3594–3598} }
 @article{kohler_friedrich_whangbo_villesuzanne_2005, title={Synthesis and characterization of [PtIn6](GeO4)(2)O and its solid solution [PtIn6](GaO4)(2-x)(GeO4)(x)O-x/2 (0 <= x <= 2): Gradual color change of the solid solution from black (x=0) to yellow (x=2) as a consequence of quantum dot effect}, volume={127}, ISSN={["1520-5126"]}, DOI={10.1021/ja053280x}, abstractNote={A new phase [PtIn6](GeO4)2O, a filled variant of [PtIn6](GaO4)2, and the solid solution [PtIn6](GaO4)2-x(GeO4)xOx/2 (0 ≤ x ≤ 2) were prepared and characterized. Single-crystal structure refinements show that [PtIn6](GeO4)2O is isotypic with the mineral, sulfohalite Na6FCl(SO4)2, and crystallizes in the space group Fm3̄m (Z = 4) with a = 1006.0(1) pm. The building units of [PtIn6](GeO4)2O are isolated [PtIn6]10+ octahedra and (GeO4)4- tetrahedra, and the isolated O2- ions occupy the centers of the In6 octahedra made up of six adjacent PtIn6 octahedra. The lattice parameter of the solid solution [PtIn6](GaO4)2-x(GeO4)xOx/2 (0 ≤ x ≤ 2) varies gradually from a = 1001.3(1) pm at x = 0 to a = 1006.0(1) pm at x = 2, and the color of the solid solution changes gradually from black (x = 0) to red (x = 1) to yellow (x = 2). The cause for the gradual color change was examined by performing density functional theory electronic structure calculations for the end members [PtIn6](GaO4)2 and [PtIn6](GeO4)2O. Our analysis indicates that an oxygen atom at the center of a In6 octahedron cuts the In 5p/In 5p bonding interactions between adjacent [PtIn6]10+ octahedra thereby raising the bottom of the conduction bands, and the resulting quantum dot effect is responsible for the color change.}, number={37}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Kohler, J and Friedrich, H and Whangbo, MH and Villesuzanne, A}, year={2005}, month={Sep}, pages={12990–12996} }
 @article{yahia_gaudin_darriet_banks_kremer_villesuzanne_whangbo_2005, title={Synthesis, crystal structure, magnetic properties, and electronic structure of the new ternary vanadate CuMnVO4}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic048244y}, abstractNote={A new magnetic oxide, CuMnVO4, was prepared, and its crystal structure was determined by single-crystal X-ray diffraction. The magnetic properties of CuMnVO4 were characterized by magnetic susceptibility and specific heat measurements, and the spin exchange interactions of CuMnVO4 were analyzed on the basis of spin-polarized electronic band structure calculations. CuMnVO4 contains MnO4 chains made up of edge-sharing MnO6 octahedra containing high-spin Mn2+ cations. Our work shows that CuMnVO4 undergoes a three-dimensional antiferromagnetic transition at approximately 20 K. Both the intrachain and interchain spin exchanges are antiferromagnetic, and the interchain spin exchange is not negligible compared to the intrachain spin exchange.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Yahia, HB and Gaudin, E and Darriet, J and Banks, M and Kremer, RK and Villesuzanne, A and Whangbo, MH}, year={2005}, month={May}, pages={3087–3093} }
 @article{xu_assoud_soheilnia_derakhshan_cuthbert_greedan_whangbo_kleinke_2005, title={Synthesis, structure, and magnetic properties of the layered copper(II) oxide Na2Cu2TeO6}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic0502832}, abstractNote={A new quaternary layered transition-metal oxide, Na2Cu2TeO6, has been synthesized under air using stoichiometric (with respect to the cationic elements) mixtures of Na2CO3, CuO, and TeO2. Na2Cu2TeO6 crystallizes in the monoclinic space group C2/m with a = 5.7059(6) Å, b = 8.6751(9) Å, c = 5.9380(6) Å, β = 113.740(2)°, V = 269.05(5) Å3, and Z = 2, as determined by single-crystal X-ray diffraction. The structure is composed of [Cu2TeO6] layers with the Na atoms located in the octahedral voids between the layers. Na2Cu2TeO6 is a green nonmetallic compound, in agreement with the electronic structure calculation and electrical resistance measurement. The magnetic susceptibility shows Curie−Weiss behavior between 300 and 600 K with an effective moment of 1.85(2) μB/CuII and ϑc = −87(6) K. A broad maximum at 160 K is interpreted as arising from short-range one-dimensional antiferromagnetic correlations. With the aid of the technique of magnetic dimers, the short-range order was analyzed in terms of an alternating chain model, with the surprising result that the stronger intrachain coupling involves a super-superexchange pathway with a Cu−Cu separation of >5 Å. The J2/J1 ratio within the alternating chain refined to 0.10(1), and the spin gap is estimated to be 127 K.}, number={14}, journal={INORGANIC CHEMISTRY}, author={Xu, JX and Assoud, A and Soheilnia, N and Derakhshan, S and Cuthbert, HL and Greedan, JE and Whangbo, MH and Kleinke, H}, year={2005}, month={Jul}, pages={5042–5046} }
 @article{cao_haraldsen_brown_musfeldt_thompson_zvyagin_krzystek_whangbo_nagler_torardi_2005, title={Understanding low-energy magnetic excitations and hydrogen bonding in VOHPO4 center dot(2H2O)-H-1}, volume={72}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.72.214421}, abstractNote={We report the variable temperature vibrational properties of single crystals of the $S=1∕2$ Heisenberg antiferromagnet $\mathrm{V}\mathrm{O}\mathrm{H}\mathrm{P}{\mathrm{O}}_{4}∙\frac{1}{2}{\mathrm{H}}_{2}\mathrm{O}$. A pair of peaks in the far infrared spectral response may be due to magnetic excitations. We invoke a dynamic Dzyaloshinskii-Moriya mechanism to explain the activation and polarization dependence of the singlet-to-triplet gap in the far infrared, and we identify the low-energy phonons that likely facilitate this coupling. The spin-gap values are compared to those obtained via magnetic susceptibility, electron spin resonance, and neutron scattering. Vibrational mode splitting in $\mathrm{V}\mathrm{O}\mathrm{H}\mathrm{P}{\mathrm{O}}_{4}∙\frac{1}{2}{\mathrm{H}}_{2}\mathrm{O}$ indicates a weak local symmetry breaking near $180\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and the low-temperature redshift of $\mathrm{V}\mathrm{O}$ and $\mathrm{H}\mathrm{O}$ related modes demonstrates enhanced low-temperature hydrogen bonding. The low lattice symmetry is important for the proposed magnetoelastic interactions.}, number={21}, journal={PHYSICAL REVIEW B}, author={Cao, J and Haraldsen, JT and Brown, S and Musfeldt, JL and Thompson, JR and Zvyagin, S and Krzystek, J and Whangbo, MH and Nagler, SE and Torardi, CC}, year={2005}, month={Dec} }
 @article{woodward_choi_musfeldt_haraldsen_wei_koo_dai_whangbo_landee_turnbull_2005, title={Understanding the color properties of (C5H9NH3)(2)CuBr4 in high magnetic fields}, volume={71}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.71.174416}, abstractNote={We report the optical and magneto-optical properties of ${({\mathrm{C}}_{5}{\mathrm{H}}_{9}\mathrm{N}{\mathrm{H}}_{3})}_{2}\mathrm{Cu}{\mathrm{Br}}_{4}$, an $S=1∕2$ low-dimensional molecular antiferromagnet. Complementary electronic structure calculations demonstrate that the color properties of this material are dominated by excitations of the $\mathrm{Cu}{\mathrm{Br}}_{4}^{2\ensuremath{-}}$ chromophore. In an applied magnetic field, ${({\mathrm{C}}_{5}{\mathrm{H}}_{9}\mathrm{N}{\mathrm{H}}_{3})}_{2}\mathrm{Cu}{\mathrm{Br}}_{4}$ displays a rich magnetochromic response that is particularly strong in the direction of the bromide-bromide bridge pairs between the chains. This effect is attributed to a field-induced reorientation of the $\mathrm{Cu}{\mathrm{Br}}_{4}^{2\ensuremath{-}}$ anions. These color changes are correlated with critical fields in the magnetization.}, number={17}, journal={PHYSICAL REVIEW B}, author={Woodward, JD and Choi, J and Musfeldt, JL and Haraldsen, JT and Wei, X and Koo, HJ and Dai, D and Whangbo, MH and Landee, CP and Turnbull, MM}, year={2005}, month={May} }
 @article{villesuzanne_whangbo_koo_2005, title={Unpaired spin populations and spin-pairing tendencies of the nonequivalent vanadium sites of the magnetic metal NaV6O11 investigated by electronic band structure calculations and spin dimer analysis}, volume={17}, ISSN={["1520-5002"]}, DOI={10.1021/cm050666y}, abstractNote={The unpaired spin populations and spin-pairing tendencies of the three different vanadium atoms of NaV6O11 above and below its trimerization temperature Tt = 245 K were examined by determining, as a function of the number of unpaired spins per formula unit, N, the total energies of NaV6O11 as well as the 3d orbital populations of the V(1), V(2), and V(3) atoms on the basis of first-principles spin-polarized electronic band structure calculations. Spin dimer analysis was also carried out to estimate the spin-pairing tendencies of the V(1) and V(2) sites above and below Tt. Our work does not support the heuristic assumptions employed to interpret the magnetic properties of NaV6O11 as well as its analogues SrV6O11 and PbV6O11. States with a wide range of N values (i.e., ∼4 < N < ∼9) are expected to contribute to the magnetic properties of NaV6O11 above and below Tt. The V(1), V(2), and V(3) atoms differ mainly in the extents of their spin polarizations but not in their oxidation states. The unpaired spin population of each V(1) site is significantly reduced by the trimerization but remains nonzero below Tt. The V(2) sites, which are present as dimer units, are not diamagnetic. The V(2) and V(3) sites each have approximately one unpaired spin per site above and below Tt.}, number={17}, journal={CHEMISTRY OF MATERIALS}, author={Villesuzanne, A and Whangbo, MH and Koo, HJ}, year={2005}, month={Aug}, pages={4344–4349} }
 @article{soulard_petit_deniard_evain_jobic_whangbo_dhaussy_2005, title={Why pressure induces an abrupt structural rearrangement in PdTe2 but not in PtTe2}, volume={178}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2005.04.008}, abstractNote={Abstract High-pressure X-ray diffraction measurements were carried out for polymeric CdI2-type compounds MTe2 (M=Pt, Pd) to investigate if they undergo a structural phase transition under pressure as does IrTe2. Up to 27 GPa at room temperature PtTe2 does not undergo any structural phase transition. In contrast, however, an abrupt change in the inter-atomic distances occurs in PdTe2 above 15.7 GPa at room temperature, and above 5 GPa at 300 °C, but the volume vs. pressure curve exhibits no discontinuity. To account for the differences between the isostructural compounds PtTe2, PdTe2 and IrTe2, their electronic structures and bonding were analyzed on the basis of first principles electronic band structure calculations.}, number={6}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Soulard, C and Petit, PE and Deniard, P and Evain, M and Jobic, S and Whangbo, MH and Dhaussy, AC}, year={2005}, month={Jun}, pages={2008–2014} }
 @article{dai_whangbo_2004, title={Classical spin and quantum-mechanical descriptions of geometric spin frustration}, volume={121}, ISSN={["0021-9606"]}, DOI={10.1063/1.1760749}, abstractNote={Geometric spin frustration (GSF) in isolated plaquettes with local spin s, i.e., an equilateral-triangle spin trimer and a regular-tetrahedron spin tetramer, was examined on the basis of classical spin and quantum-mechanical descriptions to clarify their differences and similarities. An analytical proof was given for how the state degeneracy and the total spin S of their ground states depend on the local spin s. The quantum-mechanical conditions for the occurrence of GSF in isolated plaquettes were clarified, and their implications were explored. Corner sharing between plaquettes and how it affects GSF in the resulting spin systems was examined.}, number={2}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Dai, DD and Whangbo, MH}, year={2004}, month={Jul}, pages={672–680} }
 @article{goubin_rocquefelte_whangbo_montardi_brec_jobic_2004, title={Experimental and theoretical characterization of the optical properties of CeO2, SrCeO3, and Sr2CeO4 containina Ce4+ (f(0)) ions}, volume={16}, ISSN={["1520-5002"]}, DOI={10.1021/cm034618u}, abstractNote={In an effort to find new UV absorbers, the optical properties of CeO2, SrCeO3, and Sr2CeO4 were examined by UV−visible diffuse reflectance measurements and electron energy-loss spectroscopy (EELS), and their electronic structures were investigated on the basis of first-principles density functional theory (DFT) calculations. The extinction coefficient k and the refractive index n determined from the loss function Im(−1/ε) by EELS were compared with the corresponding quantities calculated from DFT calculations. The UV absorption thresholds of these materials were determined by the electron excitation from the O 2p anionic band to the empty Ce 4f orbitals. The calculated and measured refractive indices were in satisfactory agreement. The applicability of CeO2, SrCeO3, and Sr2CeO4 as potential UV absorbers was assessed.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Goubin, F and Rocquefelte, X and Whangbo, MH and Montardi, Y and Brec, R and Jobic, S}, year={2004}, month={Feb}, pages={662–669} }
 @article{soulard_rocquefelte_petit_evain_jobic_itie_munsch_koo_whangbo_2004, title={Experimental and theoretical investigation on the relative stability of the PdS2- and pyrite-type structures of PdSe2}, volume={43}, DOI={10.1021/ic035396}, number={6}, journal={Inorganic Chemistry}, author={Soulard, C. and Rocquefelte, X. and Petit, P. E. and Evain, M. and Jobic, S. and Itie, J. P. and Munsch, P. and Koo, H. J. and Whangbo, M. H.}, year={2004}, pages={1943–1949} }
 @article{ammar_menetrier_villesuzanne_matar_chevalier_etourneau_villeneuve_rodriguez-carvajal_koo_smirnov_et al._2004, title={Investigation of the electronic and structural properties of potassium hexaboride, KB6, by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations}, volume={43}, ISSN={["1520-510X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3843112209&partnerID=MN8TOARS}, DOI={10.1021/ic049444c}, abstractNote={The electronic and structural properties of potassium hexaboride, KB6, were examined by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations. The valence bands of KB6 are partially empty, but the electrical resistivity of KB6 reveals that it is not a normal metal. The magnetic susceptibility as well as EPR and NMR measurements show the presence of localized electrons in KB6. The EPR spectra of KB6 have two peaks, a broad (∼320 G) and a narrow (less than ∼27 G) line width, and the temperature-dependence of the magnetic susceptibility of KB6 exhibits a strong hysteresis below 70 K. The temperature-dependent crystal structure determination of KB6 shows the occurrence of an unusual variation in the unit cell parameter hence supporting that the hysteresis of the magnetic susceptibility is a bulk phenomenon. The line width ΔHpp of the broad EPR signal is independent of temperature and EPR frequency. This finding indicates that the line broadening results from the dipole−dipole interaction, and the spins responsible for the broad EPR peak has the average distance of ∼1.0 nm. To explain these apparently puzzling properties, we examined a probable mechanism of electron localization in KB6 and its implications.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Ammar, A and Menetrier, M and Villesuzanne, A and Matar, S and Chevalier, B and Etourneau, J and Villeneuve, G and Rodriguez-Carvajal, J and Koo, HJ and Smirnov, AI and et al.}, year={2004}, month={Aug}, pages={4974–4987} }
 @article{dai_koo_whangbo_2004, title={Investigation of the incommensurate and commensurate magnetic superstructures of LiCuVO4 and CuO on the basis of the isotropic spin exchange and classical spin approximations}, volume={43}, ISSN={["1520-510X"]}, DOI={10.1021/ic035314c}, abstractNote={The spin lattices of magnetic oxides LiCuVO(4) and CuO are made up of CuO(2) ribbon chains. The incommensurate and commensurate magnetic superstructures of these oxides were examined by calculating the total spin exchange interaction energies of their long-range order spin arrangements on the basis of the isotropic spin exchange and classical spin approximations. The incommensurate superstructure (0, 0.532, 0) of LiCuVO(4) was analyzed to find that the next-nearest-neighbor spin exchange interaction J(nnn) is more strongly antiferromagnetic than the nearest-neighbor spin exchange interaction J(nn) in the CuO(2) chains. With this finding, we reassessed the relative strengths of the spin exchange interactions of LiCuVO(4) and CuO and then analyzed the relative energies of their long-range order spin arrangements. The incommensurate superstructure (0, 0.532, 0) of LiCuVO(4) is explained when the J(nn)/J(nnn) ratio is -0.40. Both the incommensurate superstructure (0.506, 0, -0.483) and the commensurate superstructure (0.5, 0, -0.5) of CuO, which occur at 231 and 212.5 K, respectively, are well explained in terms of the calculated total spin exchange interaction energies. The incommensurate superstructure of CuO becomes commensurate by a slight change in one interchain spin exchange interaction, which is due probably to a slight structure change brought about by the temperature lowering.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Dai, D and Koo, HJ and Whangbo, MH}, year={2004}, month={Jun}, pages={4026–4035} }
 @article{rocquefelte_goubin_koo_whangbo_jobic_2004, title={Investigation of the origin of the empirical relationship between refractive index and density on the basis of first principles calculations for the refractive indices of various TiO2 phases}, volume={43}, ISSN={["1520-510X"]}, DOI={10.1021/ic035383r}, abstractNote={On the basis of first principles electronic structure calculations, we determined the dielectric functions, the refractive indices, and the extinction coefficients of the seven different phases of TiO2 and then examined why the refractive index is related to the density by the empirical Glastone−Dale equation. The zero frequency limit of the refractive index, n0, is found to be a good approximation for the refractive index n determined around 2 eV. Our study indicates that the major factor influencing n in a series of closely related systems is the structure compactness. This finding suggests a way of preparing new UV absorbers with low refractive index.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Rocquefelte, X and Goubin, F and Koo, HJ and Whangbo, MH and Jobic, S}, year={2004}, month={Apr}, pages={2246–2251} }
 @article{soulard_rocquefelte_evain_jobic_koo_whangbo_2004, title={Investigation of the relative stabilities of various allotropic phases of elemental tellurium under pressure and their interconversion paths by electronic structure calculations and crystal structure analyses}, volume={177}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2004.08.040}, abstractNote={Elemental tellurium adopts a number of different structures under pressure. The relative stabilities of these allotropes and the interconversion between them were examined on the basis of first principles electronic band structure calculations with and without external pressure. The relative stabilities of the allotropes were also analyzed by estimating the overall strength of covalent bonding on the basis of the Te-Te overlap populations determined from tight-binding electronic structure calculations. The crystal structures of the allotropes were analyzed to determine how one form can transform into another form under pressure. Our study leads to the energy profile of tellurium as a function of pressure consistent with experiment, shows that the relative stabilities of the allotropic phases of Te are mainly governed by the overall strength of covalent bonding, and that all the allotropes are intimately related in structure, and one form can be readily converted to another form under pressure via a simple interconversion path.}, number={12}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Soulard, C and Rocquefelte, X and Evain, M and Jobic, S and Koo, H and Whangbo, MH}, year={2004}, month={Dec}, pages={4724–4731} }
 @article{choi_woodward_musfeldt_wei_whangbo_he_jin_mandrus_2004, title={Magneto-optical properties of Li0.9Mo6O17: Color change in applied magnetic field}, volume={70}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.70.085107}, abstractNote={The polarized magneto-optical response of ${\mathrm{Li}}_{0.9}{\mathrm{Mo}}_{6}{\mathrm{O}}_{17}$ was measured in order to investigate the effect of a high magnetic field on the optical properties of a quasi-one-dimensional conductor. The observed magnetochromic effect is attributed to field-induced changes in the density of states near the Fermi level and is manifest in both $\mathrm{Mo}\phantom{\rule{0.3em}{0ex}}d\ensuremath{\rightarrow}d$ on-site and $\mathrm{O}\phantom{\rule{0.3em}{0ex}}p\ensuremath{\rightarrow}\mathrm{Mo}\phantom{\rule{0.3em}{0ex}}d$ charge transfer excitations. The observed polarization dependence of the field-induced color change is consistent with the low energy scale of this effect.}, number={8}, journal={PHYSICAL REVIEW B}, author={Choi, J and Woodward, JD and Musfeldt, JL and Wei, X and Whangbo, MH and He, J and Jin, R and Mandrus, D}, year={2004}, month={Aug} }
 @article{manson_schlueter_koo_whangbo_2004, title={Reexamination of the magnetic properties of Cu-2(dca)(4)(2,5-me(2)pyz) {dca = dicyanamide; me(2)pyz = dimethylpyrazine}: isolated spin-1/2 dimers versus long-range magnetic ordering}, volume={43}, ISSN={["0020-1669"]}, DOI={10.1021/ic0354769}, abstractNote={The magnetic properties of Cu2(dca)4(2,5-me2pyz) have been reexamined. The extended structure of Cu2(dca)4(2,5-me2pyz) can be viewed in terms of Cu2(2,5-me2pyz)4+ dimer units interconnected via μ1,5-dca ligands. The bulk magnetic susceptibility χ(T) and the isothermal M(H) of Cu2(dca)4(2,5-me2pyz) are shown to be well described by an isolated dimer model. This finding was confirmed by carrying out a spin dimer analysis based on tight-binding calculations, which shows that the 2,5-me2pyz ligand provides a substantial spin exchange interaction between the Cu2+ ions while the dca ligands do not.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Manson, JL and Schlueter, JA and Koo, HJ and Whangbo, MH}, year={2004}, month={Jun}, pages={4007–4011} }
 @article{whangbo_dai_koo_2004, title={Spin dimer and classical spin analyses of the ordered magnetic structures of alkali iron pyrophosphates NaFeP2O7 and LiFeP2O7}, number={19}, journal={Dalton Transactions (Cambridge, England : 2003)}, author={Whangbo, M. H. and Dai, D. and Koo, H. J.}, year={2004}, pages={3019–3025} }
 @article{shikano_kremer_ahrens_koo_whangbo_darriet_2004, title={Synthesis and characterization of a magnetic semiconductor Na2RuO4 containing one-dimensional chains of RU6+}, volume={43}, number={1}, journal={Inorganic Chemistry}, author={Shikano, M. and Kremer, R. K. and Ahrens, M. and Koo, H. J. and Whangbo, M. H. and Darriet, J.}, year={2004}, pages={07-} }
 @article{goubin_guenee_deniard_koo_whangbo_montardi_jobic_2004, title={Synthesis, optical properties and electronic structures of polyoxometalates K3P(Mo1-xWx)(12)O-40 (0 <= x <= 1)}, volume={177}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2004.08.046}, abstractNote={Various compositions of solid solutions K3P(Mo1−xWx)12O40 (0⩽x⩽1) were prepared using two solid state synthetic routes. The crystallite size was determined by linewidth refinements of X-ray diffraction patterns using the Warren–Averbach method, and the grain size distribution by laser scattering experiments. Optical properties were determined by diffuse reflectance measurements in the UV-visible range. The optical gap Eg was found to increase exponentially from ∼2.5 to ∼3.30 eV with increasing x, and is systematically shifted to a higher energy when the grain size decreases. The relation between Eg and x was analyzed by calculating the HOMO-LUMO gaps of the [P(Mo1−xWx)12O40]3− anions on the basis of tight-binding electronic structure calculations.}, number={12}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Goubin, F and Guenee, L and Deniard, P and Koo, HJ and Whangbo, MH and Montardi, Y and Jobic, S}, year={2004}, month={Dec}, pages={4528–4534} }
 @article{whangbo_koo_dai_villesuzanne_2003, title={A discussion on the apparently puzzling structural, electrical and magnetic properties of BaVS3}, volume={175}, ISSN={["0022-4596"]}, DOI={10.1016/S0022-4596(03)00346-3}, abstractNote={The ternary vanadium sulfide BaVS3 consists of VS3 chains made up of face sharing VS6 octahedra, and exhibits a number of structural, electrical and magnetic properties that are not explained in terms of the normal metallic state. Our analysis indicates that the spin ordering of BaVS3 taking place below 30 K is most probably random along the chain direction. Thus the puzzling properties of BaVS3 are explained in terms of the broken-symmetry electronic state in which pairs of nonmagnetic V atoms alternate with those of magnetic V atoms in each VS3 chain. The origin of this broken-symmetry state was discussed on the basis of cooperative Jahn–Teller distortion and lattice strain.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Dai, D and Villesuzanne, A}, year={2003}, month={Nov}, pages={384–388} }
 @article{dai_koo_whangbo_2003, title={Analysis of the spin exchange interactions of ferromagnetic CdVO3 in terms of first principles and qualitative electronic structure calculations}, volume={175}, ISSN={["0022-4596"]}, DOI={10.1016/S0022-4596(03)00307-4}, abstractNote={Abstract First principles spin-polarized electronic band structure calculations were carried out for three ordered spin states of CdVO 3 , and the strengths of its corner- and edge-sharing spin exchange interactions were estimated. To gain insight into why CdVO 3 exhibits ferromagnetism while CaV 2 O 5 does not despite their apparent structural similarity, the spin exchange interactions of CdVO 3 and CaV 2 O 5 were compared in terms of spin dimer analysis using extended Huckel tight binding calculations, and the local geometries of their V 4+ ions were examined.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Dai, D and Koo, HJ and Whangbo, MH}, year={2003}, month={Nov}, pages={341–347} }
 @article{manson_lecher_gu_geiser_schlueter_henning_wang_schultz_koo_whangbo_2003, title={Cu(HCO2)(2)L {L = pyrazine, 4,4 '-bipyridine}: employing the formate anion as a building block in three-dimensional coordination polymers}, ISSN={["1477-9234"]}, DOI={10.1039/b302631k}, abstractNote={The formate anion, HCO2−, has been used infrequently as a building block in molecular magnetic materials. We have synthesized and structurally and magnetically characterized two new Cu(HCO2)2L compounds, where L represents pyrazine (pyz) and 4,4′-bipyridine (bipy). The single crystal structure of Cu(HCO2)2(pyz), 1, has been established by both X-ray (295 K) and neutron diffraction (20 K). The compound consists of tetragonally-elongated CuN2O4 octahedra made up of four bridging formate anions and two neutral pyz ligands. The 3D polymeric network is comprised of 2D Cu(HCO2)2 layers that are fused together by the linear pyz spacers, which form Cu–pyz-Cu chains. Cu(HCO2)2(bipy), 2, is chiral and has a more complex framework than 1. The CuO4N2 octahedra align in two unique orientations relative to one another, owing to the 41 and 21 screw axes that lie along the a and b-axes. The octahedra are connected via four bridging HCO2− anions and two bridging bipy ligands, resulting in a unique 3D scaffold structure. The magnetic behavior of 1 and 2 indicates antiferro- and ferromagnetic interactions, respectively, and the exchange couplings in both 1 and 2 are well reproduced by a 1D spin Hamiltonian. Spin dimer analysis was carried out to evaluate the relative strengths of the various spin exchange paths. It is found that the interaction through HCO2− is comparatively weak, and the strong Cu2+ spin exchange interactions are mediated by the pyz and bipy ligands via the σ-pathway. A possible reason as to why 2 displays ferromagnetic coupling is proposed.}, number={14}, journal={DALTON TRANSACTIONS}, author={Manson, JL and Lecher, JG and Gu, JY and Geiser, U and Schlueter, JA and Henning, R and Wang, XP and Schultz, AJ and Koo, HJ and Whangbo, MH}, year={2003}, pages={2905–2911} }
 @article{whangbo_koo_dai_jung_2003, title={Interpretation of the magnetic structures of Cu2Te2O5X2 (X = Cl, Br) and Ca3.1Cu0.9RuO6 on the basis of electronic structure considerations: Cases for strong super-superexchange interactions involving Cu2+ ions}, volume={42}, DOI={10.1021/ic020551}, number={12}, journal={Inorganic Chemistry}, author={Whangbo, M. H. and Koo, H. J. and Dai, D. and Jung, D.}, year={2003}, pages={3898–3906} }
 @article{koo_whangbo_lee_2003, title={Investigation of the spin exchange interactions and magnetic structures of the CrVO4-type transition metal phosphates, sulfates, and vanadates by spin dimer analysis}, volume={42}, ISSN={["0020-1669"]}, DOI={10.1021/ic030115e}, abstractNote={The CrVO(4)-type magnetic oxides MM'O(4) consist of edge-sharing MO(4) octahedral chains condensed with M'O(4) tetrahedra and exhibit a wide variety of magnetic structures. The magnetic properties of these oxides were examined by studying their spin exchange interactions on the basis of spin dimer analysis. The nature and magnitudes of the intra- and interchain spin exchange interactions depend on the square-to-rectangle distortion in the basal planes of the MO(4) chain and on the difference between the M 3d and O 2p orbital energies. The spiral magnetic structures of beta-CrPO(4) and MnSO(4) originate from the pseudohexagonal arrangement of the MO(4) chains and the frustrated interchain antiferromagnetic interactions.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH and Lee, K}, year={2003}, month={Sep}, pages={5932–5937} }
 @article{whangbo_dai_koo_jobic_2003, title={Investigations of the oxidation states and spin distributions in Ca3Co2O6 and Ca3CoRhO6 by spin-polarized electronic band structure calculations}, volume={125}, ISSN={["1879-2766"]}, DOI={10.1016/S0038-1098(02)00872-4}, abstractNote={Spin-polarized electronic band structure calculations were carried out for the magnetic solids Ca3CoMO6 (M=Co, Rh), and the local electronic structures of their transition metal atoms at the octahedral and trigonal prism sites were examined. Our calculations show that Ca3CoMO6 (M=Co, Rh) has four unpaired spins per formula unit, the magnetic moment comes predominantly from the trigonal prism site, and the metal atoms of both the octahedral and trigonal prism sites have the oxidation state +3.}, number={7-8}, journal={SOLID STATE COMMUNICATIONS}, author={Whangbo, MH and Dai, D and Koo, HJ and Jobic, S}, year={2003}, month={Feb}, pages={413–417} }
 @article{koo_whangbo_2003, title={Magnetic superstructures of cupric oxide CuO as ordered arrangements of one-dimensional antiferromagnetic chains}, volume={42}, ISSN={["0020-1669"]}, DOI={10.1021/ic020576k}, abstractNote={In cupric oxide CuO, each Cu(2+) ion has 12 nearest-neighbor Cu(2+) ions grouped into six pairs related by inversion symmetry. The relative strengths of the Cu-O-Cu superexchange interactions in cupric oxide CuO were estimated by spin dimer analysis to confirm that the strongest superexchange interactions form one-dimensional antiferromagnetic chains along the [101] direction, and the remaining interactions are weak. We analyzed ordered arrangements of these one-dimensional antiferromagnetic chains to examine why the antiferromagnetic phase transition of CuO below 212.5 K adopts a (2a, b, 2c) superstructure. The local spin arrangement around each Cu(2+) ion is more balanced in the ordered spin structures leading to a (2a, b, 2c) supercell than in any other ordered spin structures.}, number={4}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2003}, month={Feb}, pages={1187–1192} }
 @article{soulard_rocquefelte_jobic_dai_koo_whangbo_2003, title={Metal-ligand bonding and rutile- versus CdI2-type structural preference in platinum dioxide and titanium dioxide}, volume={175}, ISSN={["0022-4596"]}, DOI={10.1016/S0022-4596(03)00323-2}, abstractNote={First principles electronic structure calculations were carried out to determine the relative stabilities of the rutile- and CdI2-type structures of platinum dioxide (PtO2) and titanium dioxide (TiO2). The orbital interactions between the transition metal d- and oxygen p-orbitals were analyzed to gain insight into why PtO2 has both the rutile- and CdI2-type structures, but TiO2 has only the rutile-type structure. The cause for the large difference in the c/a ratios of the CdI2-type structures of TiO2 and PtO2 was examined.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Soulard, C and Rocquefelte, X and Jobic, S and Dai, D and Koo, HJ and Whangbo, MH}, year={2003}, month={Nov}, pages={353–358} }
 @misc{whangbo_koo_dai_2003, title={Spin exchange interactions and magnetic structures of extended magnetic solids with localized spins: theoretical descriptions on formal, quantitative and qualitative levels}, volume={176}, ISSN={["1095-726X"]}, DOI={10.1016/S0022-4596(03)00273-1}, abstractNote={Low-energy excitation energies of a magnetic solid with localized spins are probed by magnetic susceptibility, neutron scattering and Raman scattering measurements, and are analyzed using a spin Hamiltonian with a set of spin exchange parameters. The nature and values of the spin exchange parameters deduced from this analysis depend on what spin exchange paths one includes in the spin Hamiltonian. In this article, we review how spin exchange interactions of magnetic solids with localized spins are described on formal, quantitative and qualitative theoretical levels, investigate antisymmetric and anisotropic interactions for general spin dimers, and discuss the spin exchange interactions and magnetic structures of various extended magnetic solids on the basis of spin dimer analysis. Strongly interacting spin exchange paths of a magnetic solid are determined by the overlap between its magnetic orbitals, so that the strongly interacting spin unit of a magnetic solid does not necessarily have the same geometrical feature as does the arrangement of its magnetic ions or spin-carrying molecules. Therefore, in interpreting results of magnetic susceptibility, inelastic neutron scattering or Raman scattering measurements, it is essential to employ a set of spin exchange parameters chosen on the basis of proper electronic structure considerations. Spin dimer analyses based on extended Hückel tight binding calculations provide a reliable and expedient means to study the relative strengths of superexchange and super-superexchange spin exchange interactions.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Dai, D}, year={2003}, month={Dec}, pages={417–481} }
 @article{dai_whangbo_2003, title={Spin exchange interactions of a spin dimer: Analysis of broken-symmetry spin states in terms of the eigenstates of Heisenberg and Ising spin Hamiltonians}, volume={118}, ISSN={["0021-9606"]}, DOI={10.1063/1.1525809}, abstractNote={We examined the eigenstates of the Heisenberg spin Hamiltonian Ĥ=−JŜ1⋅Ŝ2 and the Ising spin Hamiltonian ĤIsing=−JŜ1zŜ2z for a general spin dimer consisting of M unpaired spins at one spin site and N unpaired spins at the other spin site, and then analyzed how the broken-symmetry spin state of a spin dimer is related to the eigenstates of Ĥ and ĤIsing. Our work shows that the description of the highest-spin and broken-symmetry spin states of a spin dimer by Ĥ is the same as that by ĤIsing. For the analysis of spin exchange interactions of a magnetic solid on the basis of density functional theory, the use of the Heisenberg spin Hamiltonian in the “cluster” approach is consistent with that of the Ising spin Hamiltonian in the “noncluster” approach.}, number={1}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Dai, DD and Whangbo, MH}, year={2003}, month={Jan}, pages={29–39} }
 @article{gauthier_jobic_evain_koo_whangbo_fouassier_brec_2003, title={Syntheses, structures, and optical properties of yellow Ce2SiS5, Ce6Si4S17, and Ce4Si3S12 materials}, volume={15}, ISSN={["0897-4756"]}, DOI={10.1021/cm0211711}, abstractNote={The Ce−S−Si system has been explored in search of new, yellow nontoxic pigments. We prepared a new Ce−S−Si phase (Ce6Si4S17), determined the crystal structures of Ce2SiS5, Ce4Si3S12, and Ce6Si4S17, and measured the chromatic properties of these Ce−S−Si phases. The differences in the yellow hue of these compounds were probed by analyzing their Ce3+ ion environments and calculating their electronic band structures. Ce6Si4S17 is distinguished from Ce2SiS5 and Ce4Si3S12 in terms of the Ce3+ structural environment and the Ce3+ 4f1→5d0 transition gap. This gap is wider for Ce6Si4S17 than for Ce2SiS5 and Ce4Si3S12 (i.e., 2.51 vs. ∼2.36 eV), and Ce6Si4S17 exhibits room-temperature luminescence whereas Ce2SiS5 and Ce4Si3S12 do not. Ce4Si3S12 and Ce6Si4S17 possess chromatic properties similar to those found for industrial pigments such as PbCrO4, BiVO4, and CdS, and show thermal and chemical stabilities.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Gauthier, G and Jobic, S and Evain, M and Koo, HJ and Whangbo, MH and Fouassier, C and Brec, R}, year={2003}, month={Feb}, pages={828–837} }
 @article{montgomery_starkey_engel_bollinger_tittelbach_schweitzer_heinen_koo_whangbo_2003, title={Synthesis of the highly ID conductor (THTTF)(4)I-19}, volume={133}, ISSN={["0379-6779"]}, DOI={10.1016/S0379-6779(02)00409-5}, abstractNote={Abstract The suitability of tetrahydrotetrathiafulvalene (THTTF) as an organic metal precursor was investigated. In general, the radical-cation salts of THTTF grew with difficulty, were of poor quality, and had low electrical conductivities. The most interesting salt that we characterized to date is (THTTF) 4 (I 5 ) 2 (I 3 )(I 2 ) 3 , which possesses a unique 1D conducting network. The X-ray structure, resistivity measurements, ESR spectra, and band calculations for (THTTF) 4 I 19 are discussed.}, journal={SYNTHETIC METALS}, author={Montgomery, LK and Starkey, KP and Engel, DB and Bollinger, J and Tittelbach, M and Schweitzer, D and Heinen, I and Koo, HJ and Whangbo, MH}, year={2003}, month={Mar}, pages={381–383} }
 @article{shultz_vostrikova_bodnar_koo_whangbo_kirk_depperman_kampf_2003, title={Trends in metal-biradical exchange interaction for first-row M-II(nitronyl nitroxide-semiquinone) complexes}, volume={125}, ISSN={["0002-7863"]}, DOI={10.1021/ja020715x}, abstractNote={We report molecular structures and temperature-dependent magnetic susceptibility data for several new metal complexes of heterospin triplet ground-state biradical ligands. The ligands are comprised of both nitronyl-nitroxide (NN) and semiquinone (SQ) spin carriers. Five compounds are five-coordinate M(II) complexes (M = Mn, Co, Ni, Cu, and Zn), and one is a six-coordinate Ni(II) complex. Five compounds were structurally characterized. During copper complex formation a reaction with methanol occurs to form a unique methoxy-substituted SQ ring. Variable-temperature magnetic susceptibility studies are consistent with strong intraligand (NN-SQ and NN-PhSQ) ferromagnetic exchange coupling. For the five-coordinate Mn, Co, and Ni complexes, the S = 1 ligand is antiferromagnetically coupled to the metal. For both the five-coordinate Cu complex and the six-coordinate Ni complex, the ligand is ferromagnetically coupled to the metal spins in accordance with orbital symmetry arguments. Despite the low molecular symmetries, the predicted trend in metal-ligand exchange interactions is supported by spin dimer analysis based on extended Hückel calculations. For (NN-SQ)NiTp(Cum,Me)() (Tp(Cum,Me)() = hydro-tris(3-cumenyl-5-methylpyrazolyl)borate), an antisymmetric exchange term was required for the best fit of the magnetic susceptibility data. Antisymmetric exchange was less important for the other complexes due to inherently smaller Deltag. Finally, it is shown that intraligand exchange coupling is of paramount importance in stabilizing high-spin states of mixed metal-biradical complexes.}, number={6}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Shultz, DA and Vostrikova, KE and Bodnar, SH and Koo, HJ and Whangbo, MH and Kirk, ML and Depperman, EC and Kampf, JW}, year={2003}, month={Feb}, pages={1607–1617} }
 @article{dai_koo_whangbo_soulard_rocquefelte_jobic_2003, title={Trends in the structure and bonding in the layered platinum dioxide and dichalcogenides PtQ(2) (Q = O, S, Se, Te)}, volume={173}, ISSN={["0022-4596"]}, DOI={10.1016/s0022-4596(03)00100-2}, abstractNote={The structure and bonding of the layered platinum dioxide and dichalcogenides PtQ2 (Q=O, S, Se, Te) were analyzed on the basis of electronic band structure calculations using the full potential linearized augmented plane wave method. We examined why the c/a ratio in PtQ2 is considerably small compared with the value expected from the consideration of closely packed Q atoms (i.e., ∼1.40 vs. 1.67), and identified the electronic factor that causes the semiconducting properties in PtO2 and PtS2, the semimetallic property in PtSe2, and the metallic property in PtTe2. To a first approximation, the oxidation states of oxygen and platinum in PtO2 can be regarded as –2 and +4, respectively, but this picture is not applicable to PtTe2. As the ligand Q is changed from O to S to Se to Te, the energy gap between the Pt 5d and the ligand p levels gradually decreases, so that the ionic character of the Pt–Q bonding in PtQ2 is gradually diminished.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Dai, D and Koo, HJ and Whangbo, MH and Soulard, C and Rocquefelte, X and Jobic, S}, year={2003}, month={Jun}, pages={114–121} }
 @article{etourneau_ammar_villesuzanne_villeneuve_chevalier_whangbo_2003, title={Unusual hysteresis in the magnetic susceptibility of cubic hexaboride KB6}, volume={42}, ISSN={["0020-1669"]}, DOI={10.1021/ic034018x}, abstractNote={Electrical resistivity, magnetic susceptibility, and electron paramagnetic resonance measurements were carried out for cubic hexaboride KB(6), which is one electron short of completely filling its conduction band. It is found that KB(6) is not metallic and has localized spins. KB(6) exhibits a highly unusual hysteresis in the magnetic susceptibility below 100 K, which suggests that it undergoes a slow relaxation process.}, number={14}, journal={INORGANIC CHEMISTRY}, author={Etourneau, J and Ammar, A and Villesuzanne, A and Villeneuve, G and Chevalier, B and Whangbo, MH}, year={2003}, month={Jul}, pages={4242–4244} }
 @article{deplano_leoni_mercuri_schlueter_geiser_wang_kini_manson_gomez-garcia_coronado_et al._2002, title={A two-dimensional radical salt based upon BEDT-TTF and the dimeric, magnetic anion [Fe(tdas)(2)](2)(2-): (BEDT-TTF)(2)[Fe(tdas)(2)] (tdas=1,2,5-thiadiazole-3,4-dithiolate)}, volume={12}, ISSN={["1364-5501"]}, DOI={10.1039/b204435h}, abstractNote={In an attempt to synthesize new synthetic metals which couple magnetic properties to conductivity, we prepared the novel salt (BEDT-TTF)2[Fe(tdas)2] [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, hereafter referred to as ET; tdas = 1,2,5-thiadiazole-3,4-dithiolate] by the electrocrystallization technique. The crystal structure of this compound, as determined by single crystal X-ray diffraction, contains conducting, organic ET layers separated by dimerized, magnetic [Fe(tdas)2]22− anions. Due to the magnetic insulating ground electronic state of the ET layer, thermally activated conductivity is observed, with a room temperature value of about 1 S cm−1. This salt was also characterized by EPR spectroscopy, dc magnetization measurements and Raman spectroscopy. The electronic structure of the ET layers was investigated by extended Hückel tight-binding calculations, and the spin exchange interactions of the ET and [Fe(tdas)2]− layers were examined by spin-dimer analysis.}, number={12}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Deplano, P and Leoni, L and Mercuri, ML and Schlueter, JA and Geiser, U and Wang, HH and Kini, AM and Manson, JL and Gomez-Garcia, CJ and Coronado, E and et al.}, year={2002}, pages={3570–3577} }
 @article{whangbo_koo_dai_villesuzanne_2002, title={Analysis of the electron localization, the anisotropy of electrical conductivity, the orbital ordering, and spin-exchange interactions in BaVS3 on the basis of first principles and semi-empirical electronic structure calculations}, volume={165}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2002.9550}, abstractNote={The electrical transport and magnetic properties of BaVS3, made up of individual VS3 octahedral chains, were examined on the basis of first principles and tight-binding electronic structure calculations. The electrical conductivity of BaVS3 is nearly isotropic despite its one-dimensional structural feature, because of the orbital interactions associated with the short S···S contacts within each VS3 chain and between adjacent VS3 chains. The probable cause for the metal–insulator transition at ∼70 K was examined in terms of first principles electronic structure calculations, which indicate that the metallic and magnetic insulating states of BaVS3 are nearly the same in energy. This is consistent with the observation that the metal–insulator transition at ∼70 K is caused by electron localization. The observed magnetic properties of BaVS3 below ∼70 K are readily explained under the assumption that the symmetry-broken t2g-orbitals act as the magnetic orbitals in the magnetic insulating state of BaVS3. The probable cause for the latter was discussed.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Dai, D and Villesuzanne, A}, year={2002}, month={May}, pages={345–358} }
 @article{zhu_musfeldt_koo_whangbo_teweldemedhin_greenblatt_2002, title={Dimensionality effects on the optical properties of (PO2)(4)(WO3)(2m) (m=2, 4, 6, 7)}, volume={14}, ISSN={["0897-4756"]}, DOI={10.1021/cm011675j}, abstractNote={We report the 300 K polarized reflectance spectra and calculated electronic band structures of a series monophosphate tungsten bronzes, (PO2)4(WO3)2m (m = 2, 4, 6, 7). These materials have several layers of corner-sharing WO6 octahedra separated by one PO4 layer, leading to an octahedral layer thickness that is “tunable” with m. In the optical regime, the spectra of the m = 2, 4, 6, and 7 materials display an anisotropic electronic excitation, originating from the W intra-t2g d → d transition. The intensity and frequency of the intra-t2g d → d excitation vary with the octahedral layer thickness. Several vibrational modes along the interlayer direction of the m = 4, 6, and 7 compounds change with m as well. These results are consistent with the lattice becoming softer with increasing m. The low-frequency electrodynamics of the monophosphate tungsten bronzes shows a gap or pseudogap feature in the infrared region, demonstrating a ubiquitous bound-carrier response in these tungsten bronzes.}, number={6}, journal={CHEMISTRY OF MATERIALS}, author={Zhu, ZT and Musfeldt, JL and Koo, HJ and Whangbo, MH and Teweldemedhin, ZS and Greenblatt, M}, year={2002}, month={Jun}, pages={2607–2615} }
 @article{whangbo_koo_dai_jung_2002, title={Effect of metal-ligand bond lengths on superexchange interactions in Jahn-Teller d(4) ion systems: Spin dimer analysis of the magnetic structure of marokite CaMn2O4}, volume={41}, ISSN={["1520-510X"]}, DOI={10.1021/ic0202458}, abstractNote={In marokite CaMn(2)O(4), all six Mn-O bonds of each MnO(6) octahedron are different because of the Jahn-Teller distortion so that every Mn(3+) (d(4)) ion has six different superexchange interactions with its neighboring Mn(3+) ions. The spin exchange interactions of CaMn(2)O(4) were examined on the basis of spin dimer analysis to find what geometrical parameters of the Mn-O-Mn superexchange paths control the signs and strengths of their spin exchange interactions. Our work correctly describes the magnetic structure of CaMn(2)O(4) observed from neutron powder diffraction measurements and shows that the antiferromagnetic interactions of the Mn-O-Mn paths depend primarily on the asymmetry and the Mn-O bond length of the Mn-O-Mn bridge, but not on the 90 degree angle Mn-O-Mn bond angle.}, number={21}, journal={INORGANIC CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Dai, D and Jung, D}, year={2002}, month={Oct}, pages={5575–5581} }
 @article{whangbo_koo_villesuzanne_pouchard_2002, title={Effect of metal-oxygen covalent bonding on the competition between Jahn-Teller distortion and charge disproportionation in the perovskites of high-spin d(4) metal ions LaMnO3 and CaFeO3}, volume={41}, DOI={10.1021/ic0110427}, abstractNote={The perovskites LaMnO(3) and CaFeO(3) consisting of high-spin d(4) transition metal ions undergo different types of distortions, i.e., a Jahn-Teller distortion in LaMnO(3) and a charge disproportionation in CaFeO(3). We investigated the electronic factor causing this difference on the basis of first principles spin-polarized electronic band structure calculations for their ideal cubic structures and also tight-binding electronic band structure calculations for their ideal cubic and distorted structures. Our study shows that a charge disproportionation is favored over a Jahn-Teller distortion in CaFeO(3) because the covalent character is strong in the Fe-O bond, while the opposite is true for LaMnO(3) because the covalent character is weak in the Mn-O bond. In spin-polarized electronic band structure calculations, the covalency of the M-O (M = Fe, Mn) bond is enhanced in the up-spin bands but is reduced in the down-spin bands. Our analysis shows that electron-electron repulsion causes the energy gap between the metal 3d and the oxygen 2p orbitals to become larger for the down-spin than for the up-spin-orbital interactions. Thus in the d-block e(g) bands of both LaMnO(3) and CaFeO(3) the metal 3d orbital contribution is larger in the down-spin than in the up-spin bands.}, number={7}, journal={Inorganic Chemistry}, author={Whangbo, M. H. and Koo, H. J. and Villesuzanne, A. and Pouchard, M.}, year={2002}, pages={1920–1929} }
 @article{rozier_galy_chelkowska_koo_whangbo_2002, title={Electrical resistivity, magnetic susceptibility, X-ray photoelectron spectroscopy, and electronic band structure studies of Cu-2.33-xV4O11}, volume={166}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2002.9609}, abstractNote={The electronic and physical properties of Cu2.33V4O11 were characterized by electrical resistivity, magnetic susceptibility and X-ray photoelectron spectroscopy (XPS) measurements and by tight-binding electronic band structure calculations. Attempts to prepare Cu2.33−xV4O11 outside its narrow homogeneity range led to a mixture of Cu2.33V4O11, CuVO3 and β-CuxV2O5. The magnetic susceptibility data show no evidence for a magnetic/structural transition around 300 K. The XPS spectra of Cu2.33V4O11 reveal the presence of mixed valence in both Cu and V. The [Cu+]/[Cu2+] ratio is estimated to be 1.11 from the Cu 2p3/2 peak areas, so [V4+]/[V5+]=0.56 by the charge balance. Our electronic structure calculations suggest that the oxidation state of the Cu ions is +2 in the channels of CuO4 tetrahedra, and +1 in the channels of linear CuO2 and trigonal planar CuO3 units. This predicts that [Cu+]/[Cu2+]=1.33 and [V4+]/[V5+]=0.50, in good agreement with those deduced from the XPS study.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Rozier, P and Galy, J and Chelkowska, G and Koo, HJ and Whangbo, MH}, year={2002}, month={Jul}, pages={382–388} }
 @article{dumas_tholence_continentino_fernandes_guimaraes_whangbo_2002, title={Electron paramagnetic resonance in the quasi-two dimensional magnetic ludwigite Fe3O2BO3}, volume={12}, ISSN={["1155-4339"]}, DOI={10.1051/jo4:20020435}, number={PR9}, journal={JOURNAL DE PHYSIQUE IV}, author={Dumas, J and Tholence, JL and Continentino, M and Fernandes, JC and Guimaraes, RB and Whangbo, MH}, year={2002}, month={Nov}, pages={351–354} }
 @article{koo_whangbo_vernooy_torardi_marshall_2002, title={Flux growth of vanadyl pyrophosphate, (VO)(2)P2O7, and spin dimer analysis of the spin exchange interactions of (VO)(2)P2O7 and vanadyl hydrogen phosphate, VO(HPO4)center dot 0.5H(2)O}, volume={41}, ISSN={["1520-510X"]}, DOI={10.1021/ic020249c}, abstractNote={Large transparent blue crystals of vanadyl pyrophosphate, (VO)(2)P(2)O(7), were grown from a phosphorus pentoxide flux, and the single-crystal X-ray structure of (VO)(2)P(2)O(7) was determined with high precision. On the basis of spin dimer analysis, we examined the spin exchange interactions of (VO)(2)P(2)O(7) and its precursor VO(HPO(4)).0.5H(2)O. Our analysis of (VO)(2)P(2)O(7) using two high-precision crystal structures shows unambiguously that the V3-V4 chain has a larger spin gap than does the V1-V2 chain and that the super-superexchange (V-O...O-V) interaction is stronger than the superexchange (V-O-V) interaction in the V3-V4 chain while the opposite is true in the V1-V2 chain. Our analysis of VO(HPO(4)).0.5H(2)O reveals that the superexchange interaction must dominate over the super-superexchange interaction, in disagreement with the conclusion from a powder neutron scattering study of VO(DPO(4)).0.5D(2)O.}, number={18}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH and VerNooy, PD and Torardi, CC and Marshall, WJ}, year={2002}, month={Sep}, pages={4664–4672} }
 @article{garlach_musfeldt_pigos_jones_olejniczak_graja_whangbo_schlueter_geiser_winter_et al._2002, title={Local and spatial disorder in beta ''-(ET)(2)SF5RSO3 solid solutions (R = CH2CF2, CHF, CHFCF2)}, volume={14}, ISSN={["1520-5002"]}, DOI={10.1021/cm010378b}, abstractNote={We report the polarized infrared reflectance spectra and optical conductivity of β‘ ‘-(ET)2SF5RSO3 superconducting (R = CH2CF2), metallic (R = CHF), and metal−insulator (R = CHFCF2) mixed crystal materials. Incorporation of chiral counterions in the superconducting matrix allows us to tune the physical and spectroscopic properties over the composition range by modulating the anion potential. We conclude that the two low-energy electronic excitations at ≈5200 and 9600 cm-1 are spectral manifestations of charge localization in the ET stack, made manifest by both local (anion pocket) and spatial (positional) disorder.}, number={7}, journal={CHEMISTRY OF MATERIALS}, author={Garlach, AD and Musfeldt, JL and Pigos, JM and Jones, BR and Olejniczak, I and Graja, A and Whangbo, MH and Schlueter, JA and Geiser, U and Winter, RW and et al.}, year={2002}, month={Jul}, pages={2969–2976} }
 @article{clayhold_ulutagay-kartin_hwu_koo_whangbo_voigt_eaiprasertsak_2002, title={Magnetic properties of the low-dimensional cuprate Na5RbCu4(AsO4)(4)Cl-2}, volume={66}, number={5}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Clayhold, J. A. and Ulutagay-Kartin, M. and Hwu, S. J. and Koo, H. J. and Whangbo, M. H. and Voigt, A. and Eaiprasertsak, K.}, year={2002}, pages={052403–1} }
 @article{el abed_gaudin_darriet_whangbo_2002, title={Magnetic susceptibility and spin exchange interactions of the hexagonal perovskite-type oxides Sr-4/3(Mn2/3Ni1/3)O-3}, volume={163}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2001.9439}, abstractNote={Magnetic susceptibility measurements were carried out for two hexagonal perovskite-type oxides Sr1+x(Mn1−xNix)O3 with slightly different compositions (i.e., x=13 and 0.324). A significant difference in the susceptibilities of the two phases demonstrates the need to control phase compositions accurately. Sr4/3(Mn2/3Ni1/3)O3 consists of two spin sublattices, i.e., the Mn4+ and the Ni2+ ion sublattices. Spin dimer analysis was carried out to examine the relative strengths in the spin exchange interactions of the Mn4+ ion sublattice. The temperature dependence of the magnetic susceptibility of Sr4/3(Mn2/3Ni1/3)O3 was found consistent with a picture in which the Mn4+ ion sublattice has weakly interacting antiferromagnetically coupled (Mn4+)2 dimers, the Ni2+ ion sublattice acts as a paramagnetic system, and the two sublattices are nearly independent.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={El Abed, A and Gaudin, E and Darriet, J and Whangbo, MH}, year={2002}, month={Feb}, pages={513–518} }
 @article{choi_musfeldt_wang_koo_whangbo_galy_millet_2002, title={Optical investigation of Na2V3O7 nanotubes}, volume={14}, ISSN={["1520-5002"]}, DOI={10.1021/cm010965x}, abstractNote={We report the electronic and vibrational properties of Na2V3O7 nanotubes and compare the response with other layered and nonlayered vanadates. The electronic structure of Na2V3O7 displays a strong similarity to that of nontubular vanadates. We assign the 1.2-eV band as a V d → d excitation and the 3.3- and 3.9-eV bands as O 2p → V 3d charge-transfer structures. Although band structure calculations predict additional fine structure in the density of states because of the tubular morphology, such features are not observed in the absorption spectrum. The vibrational spectrum displays triplet mode splitting as a result of reduced site symmetry, consistent with the three sightly different vanadium atoms that form the basic structural unit. A low-frequency rattling mode is observed in Na2V3O7 at 88 cm-1. This unique characteristic of the Na+-ion intercalated tubes might be connected with the ionic conductivity.}, number={2}, journal={CHEMISTRY OF MATERIALS}, author={Choi, J and Musfeldt, JL and Wang, YJ and Koo, HJ and Whangbo, MH and Galy, J and Millet, P}, year={2002}, month={Feb}, pages={924–930} }
 @article{whangbo_koo_2002, title={Orbital interaction analysis of cooperative Jahn-Teller distortion, orbital ordering, spin ordering, and spin exchange interactions in magnetic solids}, volume={4}, ISSN={["1873-3085"]}, DOI={10.1016/S1293-2558(01)01261-4}, abstractNote={The phenomena of cooperative Jahn–Teller distortion, orbital ordering and spin exchange in magnetic solids were examined in terms of orbital interactions between adjacent spin sites. Cooperative Jahn–Teller distortion and orbital ordering of a magnetic solid occur to minimize the two-electron two-orbital destabilizing interactions between adjacent spin sites. The magnetic structures of cubic perovskites KCuF3, LaMnO3 and YVO3 are well accounted for in terms of the spin exchange interactions associated with their ordered magnetic orbitals.}, number={3}, journal={SOLID STATE SCIENCES}, author={Whangbo, MH and Koo, HJ}, year={2002}, month={Mar}, pages={335–346} }
 @article{anokhina_day_meyer_strobele_kauzlarich_kim_whangbo_lachgar_2002, title={Preparation, structure, and properties of a series of anisotropic oxychloride cluster compounds A(x)Nb(6)Cl(12)O(2) (A=K, Rb, Cs, or In)}, volume={338}, ISSN={["1873-4669"]}, DOI={10.1016/S0925-8388(02)00234-7}, abstractNote={In the course of our investigation aimed at the preparation of anisotropic cluster materials using a combination of oxide and chloride ligands to induce directional bonding preferences in the cluster unit, a series of niobium oxychloride cluster compounds AxNb6Cl12O2 (A=K, x=0.72(2); A=Rb, x=0.736(7); A=Cs, x=0.938(4); A=In, x=0.634(8)) was obtained by solid state synthesis. The cluster framework is based on (Nb6Cl10iO2i)Cl4aO2a clusters connected via oxide ligands in the a→ direction with two Nb–O linkages between adjacent clusters, which resembles intercluster bonding in Chevrel–Sergent phases, while in the other two directions, the linkages occur through single Cla–a bridges. The framework generates channels where the cations A+ are located. The electronic band structure of the series features a narrow partially occupied band originating from a Nb–Nb bonding state. Magnetic and ESR measurements show the presence of localized unpaired electrons, and resistivity measurements indicate a semiconducting behavior.}, number={1-2}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Anokhina, EV and Day, CS and Meyer, HJ and Strobele, M and Kauzlarich, SM and Kim, H and Whangbo, MH and Lachgar, A}, year={2002}, month={May}, pages={218–228} }
 @article{whangbo_koo_2002, title={Spin dimer analysis of the spin exchange interactions in paramelaconite Cu4O3 and its analogue Ag2Cu2O3 and the spin ordering of the Cu2O3 spin lattice leading to their magnetic phase transitions}, volume={41}, ISSN={["1520-510X"]}, DOI={10.1021/ic020141x}, abstractNote={The magnetic structures of the Cu(2)O(3) spin lattices present in Cu(4)O(3) and Ag(2)Cu(2)O(3) were analyzed by studying their spin exchange interactions on the basis of spin dimer analysis. Calculations of spin exchange parameters were calibrated by studying LiCuVO(4) whose intrachain and interchain antiferromagnetic spin exchange parameters are known experimentally. The magnetic phase transition of Cu(4)O(3) at 42.3 K doubles the unit cell along each crystallographic direction. The spin arrangements of the Cu(2)O(3) lattice consistent with this experimental observation are different from conventional antiferromagnetic ordering. Our analysis indicates that spin fluctuation should occur in Cu(4)O(3), low-dimensional magnetism should be more important than magnetic frustration in Cu(4)O(3), and Ag(2)Cu(2)O(3) and Cu(4)O(3) should have similar structural and magnetic properties.}, number={13}, journal={INORGANIC CHEMISTRY}, author={Whangbo, MH and Koo, HJ}, year={2002}, month={Jul}, pages={3570–3577} }
 @misc{koo_whangbo_lee_2002, title={Spin dimer analysis of the three-dimensional antiferromagnetic ordering in the quaternary manganese sulfides BaLn(2)MnS(5) (Ln = La, Ce, Pr)}, volume={169}, ISSN={["1095-726X"]}, DOI={10.1016/S0022-4596(02)00021-X}, abstractNote={The quaternary manganese sulfides BaLn2MnS5 (Ln=La, Ce, Pr) consist of (MnS4)6− anions separated with short S⋯S distances slightly longer than the van der Waals distance. Nevertheless, these sulfides are known to undergo a three-dimensional (3D) antiferromagnetic ordering at a reasonably high temperature (i.e., TN=58.5, 62.0 and 64.5 K for Ln=La, Ce and Pr, respectively). The origin of this observation was probed by studying the Mn–S⋯S–Mn super–superexchange interactions of BaLn2MnS5 on the basis of spin dimer analysis. The non-bonding S⋯S contacts in the vicinity of the van der Waals distance are found essential in determining the strengths of the Mn–S⋯S–Mn super–superexchange interactions. The antiferromagnetic spin exchange between adjacent (MnS4)6− anions along the c-direction (J2) is calculated to be stronger than that in the ab-plane (J1) by a factor of ∼10, so that the strongly interacting spin units of BaLn2MnS5 (Ln=La, Ce, Pr) are 1D chains made up of the exchange paths J2. The relative strengths of the spin exchange interactions for the J1 and J2 paths are consistent with the finding that the Néel temperatures of BaLn2MnS5 are reasonably high, and they increase in the order BaLa2MnS5<BaCe2MnS5< BaPr2MnS5.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH and Lee, KS}, year={2002}, month={Dec}, pages={143–148} }
 @article{whangbo_koo_dumas_continentino_2002, title={Theoretical investigation of the spin exchange interactions and magnetic properties of the homometallic ludwigite Fe3O2BO3}, volume={41}, ISSN={["1520-510X"]}, DOI={10.1021/ic010956q}, abstractNote={The homometallic ludwigite Fe(3)O(2)BO(3) has a complex structure made up of corner- and edge-sharing FeO(6) octahedra and exhibits a number of apparently puzzling magnetic properties. The reasons for these properties were probed by examining the trends in the spin exchange interactions of Fe(3)O(2)BO(3). To analyze the relative strengths of spin exchange interactions in such a complex magnetic solid, we first generalized the method of spin dimer analysis and then employed the resulting formulation to investigate how the magnetic properties of Fe(3)O(2)BO(3) are related to its reported crystal structures. The spin-orbital interaction energies calculated for various spin dimers of Fe(3)O(2)BO(3) provide estimates for the relative strengths of the associated spin exchange interactions, which in turn account for the observed magnetic properties of Fe(3)O(2)BO(3).}, number={8}, journal={INORGANIC CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Dumas, J and Continentino, MA}, year={2002}, month={Apr}, pages={2193–2201} }
 @article{schlueter_geiser_wang_kini_ward_parakka_daugherty_kelly_nixon_winter_et al._2002, title={Trifluoromethylsulfonyl-based salts of BEDT-TTF: Crystal and electronic structures and physical properties}, volume={168}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2002.9750}, abstractNote={Three 2 : 1 salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) with trifluoromethylsulfonyl-based anions N(SO2CF3)2−, CH(SO2CF3)2− and C(SO2CF3)3− were prepared by electrocrystallization. These salts were characterized by single-crystal X-ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistivity measurements and electronic band structure calculations. (ET)2N(SO2CF3)2 is a two-dimensional (2D) metal, but its ESR spin susceptibility above 150 K shows a weakly semiconducting behavior, presumably because during ESR measurements the sample cooling rate is slow hence allowing the disordered anions to readjust their positions. (ET)2CH (SO2CF3)2 is a 2D metal and undergoes a metal-to-insulator (MI) transition at 110 K due probably to a geometry change of the donor molecule layers. (ET)2C(SO2CF3)3 is a one-dimensional (1D) metal and undergoes an MI between 180 and 240 K, which is expected to be of charge density wave type.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Schlueter, JA and Geiser, U and Wang, HH and Kini, AM and Ward, BH and Parakka, JP and Daugherty, RG and Kelly, ME and Nixon, PG and Winter, RW and et al.}, year={2002}, month={Nov}, pages={524–534} }
 @article{koo_seo_whangbo_2001, title={Consequence of the metal-atom clustering on the magnetic properties in vanadium sulfide V5S8}, volume={160}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2001.9260}, abstractNote={On the basis of qualitative bonding considerations and tight-binding electronic band structure calculations, we examined how the unequal spin moment distribution is related to the metal-atom clustering in V5S8 and why V5S8 exhibits both localized and itinerant magnetic properties.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Seo, DK and Whangbo, MH}, year={2001}, month={Aug}, pages={287–291} }
 @article{schlueter_ward_geiser_wang_kini_parakka_morales_koo_whangbo_winter_et al._2001, title={Crystal structure, physical properties and electronic structure of a new organic conductor beta ''-(BEDT-TTF)(2)SF5CHFCF2SO3}, volume={11}, ISSN={["0959-9428"]}, DOI={10.1039/b008735l}, abstractNote={A new organic conductor, β″-(BEDT-TTF)2SF5CHFCF2SO3 [BEDT-TTF, hereafter abbreviated ET, refers to bis(ethylenedithio)tetrathiafulvalene], was prepared by electrocrystallization. The crystal structure of this salt was determined by single crystal X-ray diffraction at 298 and 150 K, its physical properties were examined by electrical resistivity, Raman spectroscopy and EPR measurements, and its electronic structure was calculated and compared with that of the analogous salt β″-(ET)2SF5CH2CF2SO3. Whereas β″-(ET)2SF5CHFCF2SO3 has disordered anions and undergoes a metal-to-insulator transition at ∼190 K, β″-(ET)2SF5CH2CF2SO3 has ordered anions and is semiconducting down to ∼100 K, metallic below ∼100 K, and superconducting below 5 K. At room temperature both β″-(ET)2SF5CHFCF2SO3 and β″-(ET)2SF5CH2CF2SO3 have similar electronic band structures and physical properties. When the temperature is lowered, each donor molecule stack becomes dimerized in both salts. However, the interdimer interaction within each donor stack nearly vanishes in β″-(ET)2SF5CHFCF2SO3, but remains substantial in β″-(ET)2SF5CH2CF2SO3.}, number={8}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Schlueter, JA and Ward, BH and Geiser, U and Wang, HH and Kini, AM and Parakka, J and Morales, E and Koo, HJ and Whangbo, MH and Winter, RW and et al.}, year={2001}, pages={2008–2013} }
 @article{jung_koo_dai_whangbo_2001, title={Electronic structure study of scanning tunneling microscopy images of the rutile TiO2(110) surface and their implications on the surface relaxation}, volume={473}, ISSN={["1879-2758"]}, DOI={10.1016/S0039-6028(00)00970-5}, abstractNote={In scanning tunneling microscopy (STM) images recorded for rutile TiO2(1 1 0) surfaces with oxygen vacancies, the non-defect-site five-coordinate Ti atoms and the vacancy sites of the bridging oxygen atom rows appear bright while the six-coordinate Ti atoms and the bridging oxygen atoms appear dark. To find what kinds of surface relaxation can cause such STM images, we carried out partial density plot calculations for the unrelaxed structure and a number of model relaxed structures of the rutile TiO2(1 1 0) surface with oxygen vacancies using the extended Hückel tight binding method. We also performed density functional theory calculations to estimate the Ti atom displacements for the three types of Ti atoms present on TiO2(1 1 0) surfaces with oxygen vacancies.}, number={3}, journal={SURFACE SCIENCE}, author={Jung, D and Koo, HJ and Dai, D and Whangbo, MH}, year={2001}, month={Feb}, pages={193–202} }
 @article{rudko_long_musfeldt_koo_whangbo_revcolevschi_dhalenne_bernholdt_2001, title={Electronic transitions in doped and undoped copper germanate}, volume={13}, ISSN={["0897-4756"]}, DOI={10.1021/cm000703f}, abstractNote={We report an analysis of the absorption edge anisotropy in CuGeO3 based on a comparison of polarized optical data with electronic structure calculations in the framework of the extended Huckel tight binding model. Taking the z axis as parallel to the CuO4 chains, we ascribe the absorption edge in the magnetic chain direction to O 2px, 2py → singly filled Cu 3d transitions and the edge in the transverse direction to O 2pz → singly filled Cu 3d excitations. The dual slope in the transverse direction is a direct consequence of the double maximum in the O 2pz density of states. The influence of Zn and Si doping on the electronic spectra of CuGeO3 is analyzed as well. Whereas neither impurity affects the phonon-assisted d−d band, Si doping smears the charge-transfer gap. This smearing of the gap by interchain impurity substitution is attributed to random distortions of the crystalline lattice giving rise to structurally induced changes in the electronic properties.}, number={3}, journal={CHEMISTRY OF MATERIALS}, author={Rudko, GY and Long, VC and Musfeldt, JL and Koo, HJ and Whangbo, MH and Revcolevschi, A and Dhalenne, G and Bernholdt, DE}, year={2001}, month={Mar}, pages={939–944} }
 @article{koo_whangbo_2001, title={Examination of the anisotropic spin exchange interactions of CuM2O6 (M = Sb, V, Nb) by spin dimer analysis}, volume={156}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2000.8969}, abstractNote={The anisotropic spin exchange interactions of the magnetic solids CuM2O6 (M=Sb, V, Nb) were explained by analyzing their reported crystal structures and calculating the spin orbital interaction energies of their spin dimers. The magnetic orbital of each Cu2+ site in CuM2O6 is given by the “x2–y2” orbital so that the magnitude of an antiferromagnetic spin exchange interaction for a given spin dimer increases when the arrangement of the nearest-neighbor square-planar CuO4 units containing the magnetic orbitals provides a good sigma overlap between the adjacent magnetic orbitals. The one-dimensional magnetic chains of α-CuV2O6, β-CuNb2O6, and α-CuNb2O6 run along a direction different than their edge-sharing CuO4 chain directions. Our study predicts that the antiferromagnetic ordering in β-CuNb2O6 should make the magnetic unit cell double the chemical unit cell along the b-direction.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2001}, month={Jan}, pages={110–116} }
 @article{gourdon_jeanneau_evain_jobic_brec_2001, title={Influence of the metal-metal sigma bonding on the structures and physical properties of the hexagonal perovskite-type sulfides Sr9/8TiS3,Sr8/7TiS3, and Sr-8/7[Ti6/7Fe1/7]S-3}, volume={162}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2001.9361}, abstractNote={The structural and electronic consequences of the metal–metal sigma bonding in the hexagonal perovskite sulfides were examined by calculating the electronic band structures of Sr9/8TiS3 and Sr8/7TiS3, by synthesizing Sr8/7[Ti6/7Fe1/7]S3 and characterizing its crystal structure, and by measuring the magnetic susceptibilities of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The (TiS3)∞ chains of Sr9/8TiS3 and Sr8/7TiS3 contain oligomer units (Oh)n (n=4, 5) made up of face-sharing TiS6 octahedra (Oh). Given the (TiS3)∞ chains aligned along the z direction, the only occupied d-block levels of each (TiS3)∞ chain are the most sigma bonding level of each (Oh)n oligomer, which is constructed from its nz2 orbitals. This “n-orbital two-electron” metal–metal sigma bonding controls the d-orbital density distribution and the Ti–Ti distances of the (Oh)n oligomers and is ultimately responsible for the semiconducting property of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The Sr8/7[Ti6/7 Fe1/7]S3 structure is described by the trigonal symmetry, R̄3m (00γ)0s superspace group with the following parameters: as=11.4935(11) Å, cs=2.9986(7) Å, q=0.57161(15) c*, and Vs=343.05(15) Å3.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Gourdon, O and Jeanneau, E and Evain, M and Jobic, S and Brec, R}, year={2001}, month={Nov}, pages={103–112} }
 @article{pigos_jones_zhu_musfeldt_homes_koo_whangbo_schlueter_ward_wang_et al._2001, title={Infrared and optical properties of beta '-(ET)(2)SF5CF2SO3: Evidence for a 45 K spin peierls transition}, volume={13}, ISSN={["0897-4756"]}, DOI={10.1021/cm000839d}, abstractNote={We measured the polarized infrared reflectance of β‘-(ET)2SF5CF2SO3 as a function of temperature and analyzed the spin-exchange interactions of this salt by calculating the spin−orbital interaction energies between adjacent spin sites. The observed changes in vibrational properties below the 45 K transition support a weak lattice distortion in combination with a spin gap in this material. The spin-exchange interaction is predicted to occur primarily along the (−a +b) diagonal direction, in good agreement with the spectral data. In addition, notable frequency shifts of vibrational modes point to a second transition between 100 and 200 K. The low-lying electronic excitation in the stack direction (assigned as a charge-transfer feature based upon our electronic band structure calculations) shows distinct changes with temperature that are consistent with trends in the vibrational spectrum. The pattern of a high-temperature transition preceding the spin-Peierls transition is discussed in relation to other low-dimensional organic and inorganic materials.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Pigos, JM and Jones, BR and Zhu, ZT and Musfeldt, JL and Homes, CC and Koo, HJ and Whangbo, MH and Schlueter, JA and Ward, BH and Wang, HH and et al.}, year={2001}, month={Apr}, pages={1326–1333} }
 @article{bar_delineau_hafele_whangbo_2001, title={Investigation of the stiffness change in, the indentation force and the hydrophobic recovery of plasma-oxidized polydimethylsiloxane surfaces by tapping mode atomic force microscopy}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/s0032-3861(00)00738-2}, abstractNote={Polydimethylsiloxane (PDMS) samples of different crosslink densities were oxidized in air plasma, and the stiffness change in the oxidized PDMS surface was monitored by performing tapping mode atomic force microscopy (TMAFM) distance-sweep measurements and numerical simulations of the cantilever equation of motion based on a contact mechanics model. The diffusion mechanism of hydrophobic recovery of an oxidized PDMS surface was examined by a combined use of TMAFM distance-sweep and phase imaging experiments. Our work shows that the modulus of the oxidized PDMS surface increases with increasing the oxidation time, and supports the diffusion mechanism of hydrophobic recovery. It is possible to extract information about the indentation force from observed indentation curves and to employ TMAFM for force modulation experiments at high modulation frequency.}, number={8}, journal={POLYMER}, author={Bar, G and Delineau, L and Hafele, A and Whangbo, MH}, year={2001}, month={Apr}, pages={3627–3632} }
 @article{manson_huang_lynn_koo_whangbo_bateman_otsuka_wada_argyriou_miller_2001, title={Long-range magnetic order in Mn[N(CN)(2)](2)(pyz) {pyz =pyrazine} susceptibility, magnetization, specific heat, and neutron diffraction measurements and electronic structure calculations}, volume={123}, DOI={10.1021/ja0024791}, abstractNote={Using dc magnetization, ac susceptibility, specific heat, and neutron diffraction, we have studied the magnetic properties of Mn[N(CN)2]2(pyz) (pyz = pyrazine) in detail. The material crystallizes in the monoclinic space group P2(1)/n with a = 7.3248(2), b = 16.7369(4), and c = 8.7905 (2) A, beta = 89.596 (2) degrees, V = 1077.65(7) A(3), and Z = 4, as determined by Rietveld refinement of neutron powder diffraction data at 1.35 K. The 5 K neutron powder diffraction data reflect very little variation in the crystal structure. Interpenetrating ReO3-like networks are formed from axially elongated Mn(2+) octahedra and edges made up of mu-bonded [N(CN)2](-) anions and neutral pyz ligands. A three-dimensional antiferromagnetic ordering occurs below T(N) = 2.53(2) K. The magnetic unit cell is double the nuclear one along the a- and c-axes, giving the (1/2, 0, 1/2) superstructure. The crystallographic and antiferromagnetic structures are commensurate and consist of collinear Mn(2+) moments, each with a magnitude of 4.15(6) mu(B) aligned parallel to the a-direction (Mn-pyz-Mn chains). Electronic structure calculations indicate that the exchange interaction is much stronger along the Mn-pyz-Mn chain axis than along the Mn-NCNCN-Mn axes by a factor of approximately 40, giving rise to a predominantly one-dimensional magnetic system. Thus, the variable-temperature magnetic susceptibility data are well described by a Heisenberg antiferromagnetic chain model, giving g = 2.01(1) and J/k(B) = -0.27(1) K. Owing to single-ion anisotropy of the Mn(2+) ion, field-induced phenomena ascribed to spin-flop and paramagnetic transitions are observed at 0.43 and 2.83 T, respectively.}, number={1}, journal={Journal of the American Chemical Society}, author={Manson, J. L. and Huang, Q. Z. and Lynn, J. W. and Koo, H. J. and Whangbo, M. H. and Bateman, R. and Otsuka, T. and Wada, N. and Argyriou, D. N. and Miller, J. S.}, year={2001}, pages={162–172} }
 @article{gourdon_evain_jobic_brec_koo_whangbo_corraze_chauvet_2001, title={On the origin of the root 7 x root 7 superstructure and the anomalous magnetic and transport properties of the layered compound Sr6V9S22O2}, volume={40}, ISSN={["0020-1669"]}, DOI={10.1021/ic001434y}, abstractNote={We examined why the 1T-VS(2) layer of the layered compound Sr(6)V(9)S(22)O(2) has the x superstructure in terms of electronic band structure calculations and metal-metal bonding across the shared edges of adjacent VS(6) octahedra. On the basis of this analysis we explored how the anomalous magnetic and transport properties of Sr(6)V(9)S(22)O(2) can be explained. Our work shows that the x superstructure is not caused by a charge density wave instability associated with Fermi surface nesting but by the metal-metal bonding through the shared edges of adjacent VS(6) octahedra. The weak and strong electron localizations observed for Sr(6)V(9)S(22)O(2) were discussed in terms of three-center two-electron and two-center two-electron V-V bonds in the 1T-VS(2) layers.}, number={12}, journal={INORGANIC CHEMISTRY}, author={Gourdon, O and Evain, M and Jobic, S and Brec, R and Koo, HJ and Whangbo, MH and Corraze, B and Chauvet, O}, year={2001}, month={Jun}, pages={2898–2904} }
 @article{whangbo_koo_lee_gourdon_evain_jobic_brec_2001, title={On the structural and electronic factors governing the magnetic properties of the hexagonal perovskite-type oxides A(x)BO(3) (A = Ca, Sr, Ba; B = Co, Ni)}, volume={160}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2001.9230}, abstractNote={The hexagonal perovskite-type oxides AxBO3 (A=Ca, Sr, Ba; B=Co, Ni) consist of (BO3)∞ chains made up of face-sharing BO6 octahedra and BO6 trigonal prisms. On the basis of molecular orbital calculations for their structural building blocks we examined why the transition metal atoms in the trigonal prisms of Sr9/7NiO3 and Sr14/11CoO3 occupy the positions away from their trigonal prism centers and why Ba6/5NiO3 and Ca3/2CoO3 exhibit apparently puzzling magnetic properties. Our analysis indicates that the structural building units of the (BO3)∞ chains in these oxides adopt high-spin states to reduce the metal–metal σ-antibonding interactions between adjacent metal atoms as well as the on-site repulsion. This finding led us to predict the number of unpaired spins that the oxides Sr9/7NiO3, Sr6/5CoO3, and Sr14/11CoO3 are expected to have.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Whangbo, MH and Koo, HJ and Lee, KS and Gourdon, O and Evain, M and Jobic, S and Brec, R}, year={2001}, month={Aug}, pages={239–246} }
 @article{olejniczak_jones_dong_pigos_zhu_garlach_musfeldt_koo_whangbo_schlueter_et al._2001, title={Optical studies of the beta ''-(ET)(2)SF5RSO3 (R=CH2CF2, CHFCF2 and CHF) system: chemical tuning of the counterion}, volume={120}, ISSN={["0379-6779"]}, DOI={10.1016/S0379-6779(00)00896-1}, abstractNote={We compare the polarized optical spectra of the organic metal β-(ET) 2 SF 5 CHFSO 3 and the β-(ET) 2 SF 5 CHCF 2 SO 3 metal/insulator material with those of the first fully organic superconductor β-(ET) 2 SF 5 CH 2 CF 2 SO 3 . The small chemical modification of the counterion has a dramatic effect on the spectral and charge transport properties of these materials, and we discuss their electronic structure in terms of band structure, many-body effects, and disorder. Based on structural differences in the anion pocket of the three salts, we conclude that the unusual electronic excitations observed in the β-(ET) 2 SF 5 CHFCF 2 SO 3 metal/insulator material are caused by disorder-related localization.}, number={1-3}, journal={SYNTHETIC METALS}, author={Olejniczak, I and Jones, BR and Dong, J and Pigos, JM and Zhu, Z and Garlach, AD and Musfeldt, JL and Koo, HJ and Whangbo, MH and Schlueter, JA and et al.}, year={2001}, month={Mar}, pages={785–786} }
 @article{koo_whangbo_coste_jobic_2001, title={Spin dimer analysis for antiferromagnetic spin exchange interactions of magnetic solids with several unpaired electrons per spin site: Trends in the spin exchange parameters of the compounds consisting of MnF5 chains and CrX2 (X = O, S) layers}, volume={156}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2000.9025}, abstractNote={For magnetic solids with several unpaired spins per spin site, the average spin orbital interaction energies 〈Δe〉 and the average spin orbital interaction energy squares 〈(Δe)2〉 were defined as a qualitative measure for the strengths of their antiferromagnetic spin exchange interactions. The trends in the antiferromagnetic spin exchange interactions of the magnetic solids containing MnF5 chains and CrX2 (X=O, S) layers were examined in terms of the 〈Δe〉 and 〈(Δe)2〉 values calculated for their spin dimers.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH and Coste, S and Jobic, S}, year={2001}, month={Feb}, pages={464–469} }
 @article{koo_whangbo_2001, title={Spin dimer analysis of the anisotropic spin exchange interactions in the distorted wolframite-type oxides CuWO4, CuMoO4-III, and Cu(Mo0.25W0.(75))O-4}, volume={40}, ISSN={["0020-1669"]}, DOI={10.1021/ic001445r}, abstractNote={The distorted wolframite-type oxides CuWO4 and CuMoO4-III have a structure in which CuO4 zigzag chains, made up of cis-edge-sharing CuO6 octahedra, run along the c-direction and hence exhibit low-dimensional magnetic properties. We examined the magnetic structures of these compounds and their isostructural analogue Cu(Mo(0.25)W0.75)O4 on the basis of the spin-orbital interaction energies calculated for their spin dimers. Our study shows that these compounds consist of two-dimensional (2D) magnetic sheets defined by one superexchange (intrachain Cu-O-Cu) and three super-superexchange (interchain Cu-O.O-Cu) paths, the strongly interacting spin units of these 2D magnetic sheets are the two-leg antiferromagnetic (AFM) ladder chains running along the (a + c)-direction, and the spin arrangement between adjacent AFM ladder chains leads to spin frustration. The similarities and differences in the magnetic structures of CuWO4, CuMoO4-III, and Cu(Mo(0.25)W0.75)O4 were discussed by examining how adjacent AFM ladder chains are coupled via the superexchange paths in the 2D magnetic sheets and how adjacent 2D magnetic sheets are coupled via another superexchange paths along the c-direction. Our study reproduces the experimental finding that the magnetic unit cell is doubled along the a-axis in CuWO(4) and along the c-axis in CuMoO4-III and predicts that the magnetic unit cell should be doubled along the a- and b-axes in Cu(Mo(0.25)W0.75)O4. In the understanding of the strength of a super-superexchange interaction, the importance of the geometrical factors controlling the overlap between the tails of magnetic orbitals was pointed out.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2001}, month={Apr}, pages={2161–2169} }
 @article{dai_whangbo_2001, title={Spin-Hamiltonian and density functional theory descriptions of spin exchange interactions}, volume={114}, ISSN={["0021-9606"]}, DOI={10.1063/1.1342758}, abstractNote={For a general spin dimer that has different numbers of unpaired electrons at the two spin sites, we examined the relationship between the spin exchange parameter J and the energy difference between the broken-symmetry and highest-spin states of the spin dimer on the basis of the spin-Hamiltonian Ĥ=−JŜ1⋅Ŝ2. The resulting relationship was shown to be a generalization of Noodleman’s formulas derived from the broken-symmetry method within density functional theory. We proposed a new method of calculating spin exchange parameters J within density functional theory on the basis of Slater’s transition state concept. The intrachain J values of magnetic solids A2MnF5 (A=Rb, Cs, NH4, Na, Li) were calculated by using the “transition-state” and Noodleman’s methods. The J values calculated by the transition-state method are in much better quantitative agreement with experiment.}, number={7}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Dai, DD and Whangbo, MH}, year={2001}, month={Feb}, pages={2887–2893} }
 @article{whangbo_koo_2001, title={Structural and electronic features of BaIrO3 causing the simultaneous occurrence of weak ferromagnetism and charge density wave formation}, volume={118}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(01)00166-1}, abstractNote={The ferromagnetic transition of BaIrO3 at 175 K is accompanied by charge density wave formation [Solid State Commun. 113 (2000) 657]. We examined the probable cause for this observation on the basis of tight-binding band electronic structure calculations for BaIrO3. In support of the experimental observation, our calculations show that BaIrO3 should be regarded as a weakly localized metal above 175 K, its t2g-block band density of states has a sharp peak at the Fermi level, and its Fermi surfaces have partially nested pieces.}, number={10}, journal={SOLID STATE COMMUNICATIONS}, author={Whangbo, MH and Koo, HJ}, year={2001}, pages={491–495} }
 @article{jobic_brec_pasturel_koo_whangbo_2001, title={Theoretical study of possible iridium ditelluride phases attainable under high pressure}, volume={162}, DOI={10.1006/jssc.2001.9341}, abstractNote={We examined the feasibility of preparing new high-pressure polymorphs of IrTe2 by determining the relative energies and unit cell volumes of known and hypothetical forms of IrTe2 on the basis of first-principles electronic band structure calculations using the Vienna ab initio simulation package (VASP). The IrTe2 polymorphs included in our analysis are three known phases, i.e., the polymeric CdI2-type, pyrite-type, and monoclinic IrTe2 phases, as well as four hypothetical phases, i.e., ramsdelite-type, pyrolusite-type, IrS2-type, and marcasite-type phases. The charge balances of these IrTe2 phases were analyzed by carrying out extended Hückel tight-binding electronic band structure calculations for the crystal structures optimized by VASP calculations.}, number={1}, journal={Journal of Solid State Chemistry}, author={Jobic, S. and Brec, R. and Pasturel, A. and Koo, H. J. and Whangbo, M. H.}, year={2001}, pages={63–68} }
 @article{gourdon_hanko_boucher_petricek_whangbo_kanatzidis_evain_2000, title={A unique distortion in K(1/3)Ba(2/3)AgTe(2): X-ray diffraction determination and electronic band structure analysis of its incommensurately modulated structure}, volume={39}, ISSN={["0020-1669"]}, DOI={10.1021/ic991457g}, abstractNote={The incommensurately modulated structure of a square Te-net, namely that of K1/3Ba2/3AgTe2, is determined from single-crystal X-ray diffraction data within a (3+1)D higher dimension formalism. The phase is shown to crystallize in the monoclinic symmetry, P2(1)(alpha 0 gamma) superspace group with the following lattice parameters: a = 4.6441(10) A, b = 4.6292(12) A, c = 23.765(9) A, and beta = 101.28(2) degrees with q = 0.3248(6)a* -0.071(8)c*, that is, in a symmetry different from that reported for the average structure (tetragonal) or that assumed from electron diffraction measurements (orthorhombic). After the introduction of a crenel function for the Te displacive description, the refinement converged to a residual factor R = 0.033 for 2583 observed reflections and 115 parameters (R = 0.024 and 0.101 for 1925 main reflections and 658 first-order satellites, respectively). The [Ag2-Te2] and the Ba/K layers are found to be only weakly modulated. The modulation of the square Te-net is, however, both substantial and unique. Namely, it results in two different units: a "V"-shaped Te3 trimer and a "W"-shaped Te5 pentamer. To examine both unit types, which are segregated in domains that aperiodically alternate within the Te layers, first principles electronic band structure calculations were carried out for three model commensurate structures using the tight-binding linear-muffin-tin-orbital method (LMTO). The calculations show that the distorted structures of V-pattern (model 2) and W-pattern (model 3) are more stable than the average structure (model 1) and that the V-pattern distortion provides a slightly larger stabilization than does the W-pattern distortion. The Fermi surface calculated for the average structure shows nesting vectors that are consistent with the occurrence of the V- and W-pattern distortions in the Te layers. However, these vectors do not predict the observed modulation vector of the incommensurately distorted structure, because the stabilization energy associated with the distortion is not mainly dominated by the energy lowering of the occupied band levels near the Fermi level.}, number={7}, journal={INORGANIC CHEMISTRY}, author={Gourdon, O and Hanko, J and Boucher, F and Petricek, V and Whangbo, MH and Kanatzidis, MG and Evain, M}, year={2000}, month={Apr}, pages={1398–1409} }
 @article{whangbo_koo_lee_2000, title={Analysis of nearest-neighbor spin exchange interactions by molecular orbital calculations: anisotropic spin exchange interactions in MV3O7 (M = Cd, Ca, Sr) and alpha '-NaV2O5}, volume={114}, DOI={10.1016/s0038-1098(99)00571-2}, abstractNote={Spin-dimer analysis was carried out for the room temperature structures of MV3O7 (M=Cd, Ca, Sr) and the 15 K structure of α′-NaV2O5 reported by Lüdecke et al. to examine the relative magnitudes of the nearest-neighbor spin exchange interactions between their unpaired spins. Our analysis explains why the magnetic susceptibility of the stripe spin structure of MV3O7 (M=Cd, Ca, Sr) exhibits a one-dimensional spin-1/2 Heisenberg chain-like behavior. Our study indicates that the 15 K crystal structure of α′-NaV2O5 is likely to have a spin gap and exhibit spin frustration. The predicted spin frustration is not consistent with the singlet ground state expected for a spin-Peierls system.}, number={1}, journal={Solid State Communications}, author={Whangbo, M. H. and Koo, H. J. and Lee, K. S.}, year={2000}, pages={27–32} }
 @article{koo_whangbo_2000, title={Analysis of the spin exchange interactions in the extended magnetic solids K2NiF4, K2CuF4, La2CuO4, Nd2CuO4, KNiF3, and KCuF3}, volume={151}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.2000.8627}, abstractNote={The spin exchange parameters J of the extended magnetic solids K2NiF4, K2CuF4, La2CuO4, Nd2CuO4, KNiF3, and KCuF3 were analyzed by examining the structures of their spin monomers and calculating the energy differences Δe in the spin levels of their spin dimers. The trends in the observed J parameters are well explained in terms of the Δe values obtained from extended Hückel molecular orbital calculations. The Δe value of a spin dimer is related only to the antiferromagnetic component of its J, but the spin dimer analysis based on Δe allows one to correlate the nature of the magnetic interaction with the structure of the spin dimer.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2000}, month={Apr}, pages={96–101} }
 @article{koo_whangbo_2000, title={Analysis of the spin exchange interactions in the three phases of vanadium pyrophosphate, (VO)(2)P2O7, in terms of spin-orbital interaction energy}, volume={39}, ISSN={["0020-1669"]}, DOI={10.1021/ic000046t}, abstractNote={The spin exchange interactions in the ambient-pressure orthorhombic (APO), high-pressure orthorhombic (HPO), and ambient-pressure monoclinic (APM) phases of the vanadium pyrophosphate, (VO)2P2O7, were analyzed by calculating the spin-orbital interaction energies delta e-delta e0 of their spin dimers. The anisotropy of the spin exchange interactions in the HPO phase is well explained by the delta e-delta e0 values. For the APO phase, the reported crystal structure does not provide accurate enough delta e-delta e0 values to conclude unambiguously which of the V1-V2 and V3-V4 chains has a larger spin gap and which of the bridged and edge-sharing spin dimers has a stronger spin exchange interaction in the V1-V2 and V3-V4 chains. The APM phase is predicted to exhibit essentially two spin gaps, with a large spin gap for the V8-V5-V7-V6 chain and a very small one for the V4-V2-V3-V1 chain.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2000}, month={Aug}, pages={3599–3604} }
 @article{bengel_jobic_moelo_lafond_rouxel_seo_whangbo_2000, title={Distribution of the Pb and Sb atoms in the (Pb, Sb)S layers of the Franckeite-type misfit compound [(Pb, Sb)S](2.28)NbS2 examined by scanning tunneling and atomic force microscopy}, volume={149}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1999.8552}, abstractNote={The distribution of the Pb and Sb atoms in the (Pb, Sb)S layers of the misfit compound [(Pb, Sb)S]2.28NbS2 was investigated by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). This compound has NaCl-type MS (M=Pb, Sb) layers (Q-layers) alternating with NbS2 layers (H-layers) in which the Nb atoms are located in slightly distorted trigonal prism sites. Both the H- and Q-layers of [(Pb, Sb)S]2.28NbS2 were imaged by STM and AFM. The atomic-scale STM and AFM images were analyzed in terms of the partial and total electron density plots calculated for the Q- and H-layers. The STM images of the Q-layers allowed us to detect all the constitutive atoms of the Q-layers with a short-range ordering of pure Pb and Sb rows in the aQ modulation direction.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Bengel, H and Jobic, S and Moelo, Y and Lafond, A and Rouxel, J and Seo, DK and Whangbo, MH}, year={2000}, month={Feb}, pages={370–377} }
 @article{koo_whangbo_picard_jobic_potel_gougeon_2000, title={Electronic band structure study of A(2)Mo(9)S(11) (A=K, Rb) and K1.8Mo9S11}, volume={155}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2000.8912}, abstractNote={The electronic band structures of A2Mo9S11 (A=K, Rb) and K1.8Mo9S11 are examined by extended Hückel tight binding calculations. K2Mo9S11 and K1.8Mo9S11 are metallic and exhibit resistivity anomalies below ∼115 and ∼80 K, respectively. The origin of these anomalies is explained in terms of their Fermi surfaces. Our study indicates that the resistivity anomalies of these compounds are caused by the partial nesting of their two-dimensional Fermi surfaces and that both K2Mo9S11 and Rb2Mo9S11 should exhibit a charge density wave phenomenon.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH and Picard, S and Jobic, S and Potel, M and Gougeon, P}, year={2000}, month={Nov}, pages={124–128} }
 @article{bar_ganter_brandsch_delineau_whangbo_2000, title={Examination of butadiene/styrene-co-butadiene rubber blends by tapping mode atomic force microscopy. Importance of the indentation depth and reduced tip-sample energy dissipation in tapping mode atomic force microscopy study of elastomers}, volume={16}, ISSN={["0743-7463"]}, DOI={10.1021/la9913699}, abstractNote={Tapping mode atomic force microscopy (TMAFM) measurements were performed for blends of two elastomers, cis-1,4-butadiene rubber (BR) and styrene-co-butadiene rubber (SBR) containing silica filler particles. To help interpret the TMAFM phase and height images of the BR/SBR blends, transmission electron microscopy (TEM) measurements were carried out for the BR/SBR blends, and dynamic mechanical analysis (DMA) as well as frequency-sweep/force-probe TMAFM measurements were carried out for BR and SBR homopolymers. TEM images show that silica filler particles of BR/SBR blends are present mainly in the SBR component, and DMA results reveal that BR has a lower glass transition temperature than does SBR. In the phase images of BR/SBR blends the less stiff component BR is brighter than is the stiffer component SBR. For the rational interpretation of TMAFM phase images of viscoelastic materials, it is crucial to consider the indentation depth of the tip into samples as well as the reduced tip−sample energy dissipation, not the total tip−sample energy dissipation. At a given set-point ratio the indentation depth is smaller on the stiffer component SBR than on the less stiff component BR, but at a given indentation depth the phase shift is larger on the stiffer component SBR. The phase shift increases almost linearly with increasing the reduced tip−sample energy dissipation. The reduced tip−sample sample energy dissipation is larger for SBR than for BR in agreement with DMA results.}, number={13}, journal={LANGMUIR}, author={Bar, G and Ganter, M and Brandsch, R and Delineau, L and Whangbo, MH}, year={2000}, month={Jun}, pages={5702–5711} }
 @misc{bar_brandsch_bruch_delineau_whangbo_2000, title={Examination of the relationship between phase shift and energy dissipation in tapping mode atomic force microscopy by frequency-sweep and force-probe measurements}, volume={444}, ISSN={["0039-6028"]}, DOI={10.1016/s0039-6028(99)00975-9}, abstractNote={The relationship between phase shift and energy dissipation in tapping mode atomic force microscopy was examined by performing frequency-sweep and force-probe experiments on polydimethylsiloxane (PDMS) samples of different cross-link densities. Phase shift is related to the reduced tip–sample energy dissipation, i.e. the fraction of the maximum energy of a tapping cantilever that is dissipated by the tip–sample interaction. The reduced tip–sample energy dissipation varies linearly with phase shift, and increases continuously as the tip–sample interaction increases. On a compliant polymer such as PDMS the tip–sample interaction dissipates only a small fraction of the power delivered to the tapping cantilever even under hard tapping conditions, so that the vibration of the tapping cantilever is well described in terms of the harmonic approximation.}, number={1-3}, journal={SURFACE SCIENCE}, author={Bar, G and Brandsch, R and Bruch, M and Delineau, L and Whangbo, MH}, year={2000}, month={Jan}, pages={L11–L16} }
 @misc{delineau_brandsch_bar_whangbo_2000, title={Harmonic responses of a cantilever interacting with elastomers in tapping mode atomic force microscopy}, volume={448}, ISSN={["1879-2758"]}, DOI={10.1016/s0039-6028(00)00045-5}, abstractNote={Abstract Frequency-sweep tapping-mode atomic force microscopy experiments were carried out on four elastomers, cis-1,4-butadiene rubber, styrene-co-butadiene rubber, natural rubber and polydimethylsiloxane to examine how well a cantilever tapping on compliant samples is described by the harmonic approximation. The amplitude curves and the phase shifts calculated for these elastomers using the harmonic approximation are in excellent agreement with the experimental values even when the tip–sample interaction is strong. When the overall tip–sample interaction is repulsive, the phase shift varies linearly with the reduced tip–sample energy dissipation because both quantities increase with increasing the tip–sample contact time. The phase shift is affected not only by the reduced tip–sample energy dissipation via the effective quality factor but also by the frequency shift.}, number={1}, journal={SURFACE SCIENCE}, author={Delineau, L and Brandsch, R and Bar, G and Whangbo, MH}, year={2000}, month={Mar}, pages={L179–L187} }
 @article{bar_delineau_brandsch_ganter_whangbo_2000, title={Hysteresis in the distance-sweep curves of elastomers and its implications in tapping mode atomic force microscopy}, volume={457}, ISSN={["1879-2758"]}, DOI={10.1016/S0039-6028(00)00414-3}, abstractNote={Distance-sweep tapping mode atomic force microscopy experiments were carried out for a cross-linked elastomer, polydimethylsiloxane (PDMS), and non-cross-linked elastomers, styrene-co-butadiene rubber (SBR) and cis-1,4-butadiene rubber (BR). The amplitude curves, A(Z), recorded for the approach and retraction cycles exhibit a strong hysteresis for SBR and BR, but a negligible hysteresis for PDMS. Nevertheless, the A(Z) curves for the approach and retraction cycles are each well described by the harmonic approximation for a wide region of tip–sample interaction. To examine the probable causes for this observation, the observed A(Z) curves were simulated by numerically solving the equation of motion for a tapping cantilever and by performing dynamical mechanical analysis experiments for SBR and BR. For the non-cross-linked elastomers SBR and BR, the sample vibration induced by the tapping cantilever is somewhat out of phase with the cantilever vibration, and the surface of the vibrating sample rises above the rest surface of the sample, thereby causing the observed hysteresis. In the region of strong tip–sample interaction, the amplitude curve A(Z) is mainly governed by the modulus of the sample, and the tapping cantilever senses the bulk property.}, number={1-2}, journal={SURFACE SCIENCE}, author={Bar, G and Delineau, L and Brandsch, R and Ganter, M and Whangbo, MH}, year={2000}, month={Jun}, pages={L404–L412} }
 @article{whangbo_koo_2000, title={Investigation of the spin exchange interactions in the nanotube system Na2V3O7 by spin dimer analysis}, volume={115}, ISSN={["1879-2766"]}, DOI={10.1016/S0038-1098(00)00258-1}, abstractNote={Abstract The relative magnitudes of the spin exchange interactions expected for the nanotubes of Na 2 V 3 O 7 were examined by identifying the spin dimers of the nanotube and calculating their spin orbital interaction energies. Our analysis indicates that the spin exchange interactions of the nanotube are not described by three-legged ladders, but by six mutually intersecting helical chains, and the magnetic properties of the nanotube in the low temperature region can be well approximated by those of a single helical chain. Each helical chain is described by four antiferromagnetc spin exchange parameters J 1 – J 4 with the repeat sequence [– J 2 – J 1 – J 3 – J 4 –] ∞ , where | J 1 |>| J 2 |>| J 3 |>| J 4 |. The nanotube is expected to have a spin gap.}, number={12}, journal={SOLID STATE COMMUNICATIONS}, author={Whangbo, MH and Koo, HJ}, year={2000}, pages={675–678} }
 @article{schiller_schmidt_balthes_schweitzer_koo_whangbo_heinen_klausa_kircher_strunz_2000, title={Investigations of the Fermi surface of a new organic metal: (BEDT-TTF)(4)[Ni(dto)(2)]}, volume={51}, ISSN={["0295-5075"]}, DOI={10.1209/epl/i2000-00329-2}, abstractNote={The Fermi surface (FS) of the new organic metal (BEDT-TTF)4[ Ni(dto)2] has been investigated by de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) experiments. In both quantum oscillations with two different frequencies Fα = 634 T and Fβ = 4245 T are observed. These results confirm the calculated FS, which consists of one-dimensional and two-dimensional parts separated by a small energy gap. It is shown that the temperature and field dependence of the oscillation amplitudes can be well described by standard Lifshitz-Kosevich theory considering the magnetic breakdown by the so-called coupled network model. Beatings of the oscillation amplitudes are observed by field-dependent dHvA and SdH experiments. They can be explained by a slightly warped FS showing that this material represents a quasi–two-dimensional electronic system. The observed beating nodes in the dHvA and SdH signals appear at different magnetic fields. This fact is discussed in terms of additional scattering mechanisms.}, number={1}, journal={EUROPHYSICS LETTERS}, author={Schiller, M and Schmidt, W and Balthes, E and Schweitzer, D and Koo, HJ and Whangbo, MH and Heinen, I and Klausa, T and Kircher, P and Strunz, W}, year={2000}, month={Jul}, pages={82–88} }
 @article{hagrman_laduca_koo_rarig_haushalter_whangbo_zubieta_2000, title={Ligand influences on the structures of molybdenum oxide networks}, volume={39}, DOI={10.1021/ic0004961}, number={19}, journal={Inorganic Chemistry}, author={Hagrman, P. J. and Laduca, R. L. and Koo, H. J. and Rarig, R. and Haushalter, R. C. and Whangbo, M. H. and Zubieta, J.}, year={2000}, pages={4311–4317} }
 @article{bartlett_essex_koo_nandhakumar_robertson_whangbo_2000, title={Molecular self-assembly on surfaces of organic conducting salts: Epitaxial monolayer films of naphthalene on the (001) surface of (TMTSF)(2)PF6}, volume={104}, ISSN={["1089-5647"]}, DOI={10.1021/jp000013z}, abstractNote={Pristine and naphthalene-adsorbed (001) surfaces of the organic conducting salt (TMTSF)(2)PF6 were examined by scanning tunneling microscopy (STM) to determine the structure of epitaxial monolayer films of naphthalene on the (001) surface. The observed STM images were interpreted by calculating partial electron density plots of the surface, and for naphthalene-adsorbed surfaces, by carrying out Monte Carlo simulations for the adsorption of a naphthalene molecule on the surface. The STM images recorded for the pristine (001) surface correspond to the cation layer of (TMTSF)2PF6, and each circular bright spot of the molecular-resolution STM images represents the three hydrogen atoms of the most protruding methyl group of a TMTSF molecule on the (001) surface. Naphthalene molecules adsorbed on this surface form a pseudomorphic (1 x 1) overlayer structure with respect to the underlying substrate. The naphthalene overlayer shows mechanical stability against etching by the scanning tip. An identical overlayer structure of naphthalene was obtained from several different preparation methods. On the cation-layer (001) surface naphthalene is adsorbed on each four-methyl-step'' defined by four methyl groups of two adjacent TMTSF molecules within each TMTSF stack.}, number={31}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Bartlett, PN and Essex, JW and Koo, HJ and Nandhakumar, IS and Robertson, N and Whangbo, MH}, year={2000}, month={Aug}, pages={7394–7402} }
 @article{jones_olejniczak_dong_pigos_zhu_garlach_musfeldt_koo_whangbo_schlueter_et al._2000, title={Optical spectra and electronic band structure calculations of beta ''-(ET)(2)SF5RSO3 (R = CH2CF2, CHFCF2, and CHF): Changing electronic properties by chemical tuning of the counterion}, volume={12}, ISSN={["1520-5002"]}, DOI={10.1021/cm000349l}, abstractNote={We report the polarized infrared reflectance spectra, optical conductivity, and electronic band structure of metallic β‘ ‘-(ET)2SF5CHFSO3 and compare our results with those of the β‘ ‘-(ET)2SF5CH2CF2SO3 superconductor and the β‘ ‘-(ET)2SF5CHFCF2SO3 metal/insulator material. We discuss the electronic structure of these organic molecular solids in terms of band structure, many-body effects, and disorder. On the basis of spectral similarities between the superconductor and metallic salts and structural differences in the anion pocket of all three, we conclude that the unusual electronic excitations observed in the β‘ ‘-(ET)2SF5CHFCF2SO3 metal/insulator material are not caused by electron correlation but are due to disorder-related localization.}, number={8}, journal={CHEMISTRY OF MATERIALS}, author={Jones, BR and Olejniczak, I and Dong, J and Pigos, JM and Zhu, ZT and Garlach, AD and Musfeldt, JL and Koo, HJ and Whangbo, MH and Schlueter, JA and et al.}, year={2000}, month={Aug}, pages={2490–2495} }
 @article{whangbo_koo_2000, title={Origin of the spin gap in sodium vanadium bronze Na9V14O35}, volume={115}, ISSN={["1879-2766"]}, DOI={10.1016/S0038-1098(00)00159-9}, abstractNote={The cause for the spin gap of Na9V14O35 was examined by identifying its spin dimers, calculating their spin orbital interaction energies and then finding a model spin Hamiltonian appropriate for Na9V14O35. In essence, the spin exchange interactions in the V10O30 chains of Na9V14O35 are equivalent to those of the fused chain of 10-node rings, where each node represents a spin site and nearest-neighbor spin exchange interactions are antiferromagnetic. To a first approximation, the energy gap between the ground and first excited states of this fused chain is the same as that of a 10-node ring. In general, the fused chain of n-node rings with even n is expected to have a spin gap.}, number={3}, journal={SOLID STATE COMMUNICATIONS}, author={Whangbo, MH and Koo, HJ}, year={2000}, pages={115–119} }
 @article{whangbo_2000, title={Perspective on "An extended Huckel theory. I. Hydrocarbons" - Hoffmann R (1963) J Chem Phys 39 : 1397-1412}, volume={103}, ISSN={["1432-881X"]}, DOI={10.1007/s002149900064}, number={3-4}, journal={THEORETICAL CHEMISTRY ACCOUNTS}, author={Whangbo, MH}, year={2000}, month={Feb}, pages={252–256} }
 @article{zhu_chowdhary_long_musfeldt_koo_whangbo_wei_negishi_inoue_sarrao_et al._2000, title={Polarized optical reflectance and electronic structure of the charge-density-wave materials eta- and gamma-Mo4O11}, volume={61}, DOI={10.1103/physrevb.61.10057}, abstractNote={We report the polarized optical reflectance spectra of $\ensuremath{\eta}$- and $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$ as a function of temperature and magnetic field. Excitations are assigned and analyzed based upon electronic band-structure calculations. The 300 K spectra of $\ensuremath{\eta}$- and $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$ show charge transfer transitions $(\mathrm{O} 2\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{Mo} 4d)$ near 4 eV, intraband $(\stackrel{\ensuremath{\rightarrow}}{d}d)$ transitions at $\ensuremath{\sim}1.5 \mathrm{eV},$ and a free carrier response at lower energy. The intraband $(\stackrel{\ensuremath{\rightarrow}}{d}d)$ transition shows strong and unusual anisotropy in the b and c directions, which is directly attributable to the dispersion relations of the lower-lying d-block bands. The effect of charge density wave formation on the optical properties of $\ensuremath{\eta}$- and $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$ is discussed and compared with related materials. The magnetic field dependence of the optical constants is determined for $\ensuremath{\eta}\ensuremath{-}{\mathrm{Mo}}_{4}{\mathrm{O}}_{11}$ and discussed in terms of field effects on the nesting vector and Fermi surface.}, number={15}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Zhu, Z. and Chowdhary, S. and Long, V. C. and Musfeldt, J. L. and Koo, H. J. and Whangbo, M. H. and Wei, X. and Negishi, H. and Inoue, M. and Sarrao, J. and et al.}, year={2000}, pages={10057–10065} }
 @article{koo_whangbo_2000, title={Spin dimer analysis of the spin exchange interactions of the vanadium oxides AV(4)O(9) (A = Ca, Sr, Cs-2, NH2(CH2)(4)NH2)}, volume={153}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.2000.8753}, abstractNote={The spin exchange interactions of the vanadium oxides AV4O9 (A=Ca, Sr, Cs2, and NH2(CH2)4NH2) were examined by calculating the spin orbital interaction energies of their spin dimers based on the extended Hückel method. The temperature Tmax at which the magnetic susceptibility maximum occurs in AV4O9 (A=Ca, Sr, Cs2, and NH2(CH2)4NH2) shows a wide variation (from 30 to 600 K) and increases in the order [NH2(CH2)4NH2]V4O9<CaV4O9<Cs2V4O9. The susceptibility at Tmax increases in the opposite order, and the room temperature susceptibility of [NH2(CH2)4NH2]V4O9 is about twice as high as the maximum susceptibility of CaV4O9. These observations were examined by estimating the magnetic excitation energies of the strongly interacting spin units of AV4O9.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={2000}, month={Sep}, pages={263–269} }
 @article{jung_koo_whangbo_2000, title={Study of the 18-electron band gap and ferromagnetism in semi- Heusler compounds by nea-spin-polarized electronic band structure calculations}, volume={527}, number={2000 Aug. 4}, journal={Journal of Molecular Structure [including Theochem]}, author={Jung, D. and Koo, H. J. and Whangbo, M. H.}, year={2000}, pages={113–119} }
 @article{jobic_brec_chateau_haines_leger_koo_whangbo_2000, title={Synthesis and crystal structure determination of a new pressure-induced iridium ditelluride phase, m-IrTe2, and comparison of the crystal structures and relative stabilities of various IrTe2 polymorphs}, volume={39}, ISSN={["0020-1669"]}, DOI={10.1021/ic000351e}, abstractNote={The new monoclinic IrTe2 phase m-IrTe2 was synthesized under pressure, and its structure was determined by X-ray powder diffraction. The relative stabilities of the three known and three hypothetical IrTe2 polymorphs were discussed on the basis of tight binding electronic band structure calculations. m-IrTe2 exhibits structural features of both CdI2- and pyrite-type IrTe2 phases and is expected to be nearly as stable as that of the CdI2-type IrTe2. The hypothetical IrS2- and ramsdellite-type IrTe2 phases are predicted to be more stable than the CdI2-type IrTe2.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Jobic, S and Brec, R and Chateau, C and Haines, J and Leger, JM and Koo, HJ and Whangbo, MH}, year={2000}, month={Sep}, pages={4370–4373} }
 @article{koo_whangbo_1999, title={Analysis of bonding and d-electron count in the transition-metal carbides and transition-metal-silicide carbides with discrete linear M-C-M units (M = Cr, Fe, Re) by electronic structure calculations}, volume={38}, ISSN={["0020-1669"]}, DOI={10.1021/ic981309a}, abstractNote={Electronic structures of the silicide carbides Tm(2)Fe(2)Si(2)C, Th(2)Re(2)Si(2)C, and ThFe(2)SiC and the carbide Ho(2)Cr(2)C(3) were calculated, using the extended Hückel tight binding method, to probe the d-electron counts of their transition metal atoms M (Cr, Fe, Re) the bonding of their linear M-C-M (M = Cr, Fe, Re) units. The nature of the short interlayer X.X (X = C, Si) bonds in Tm(2)Fe(2)Si(2)C, Th(2)Re(2)Si(2)C, and Ho(2)Cr(2)C(3) was also examined. Our study shows that the M-C bonds of the M-C-M units exist as double bonds. There is significant bonding in the interlayer Si.Si contacts of the silicide carbides R(2)M(2)Si(2)C (M = Fe, Re). The transition-metal atoms exist as d(10) ions in Tm(2)Fe(2)Si(2)C and Th(2)Re(2)Si(2)C. The d-electron count is slightly lower than d(10) in ThFe(2)SiC and close to d(5) in Ho(2)Cr(2)C(3).}, number={9}, journal={INORGANIC CHEMISTRY}, author={Koo, HJ and Whangbo, MH}, year={1999}, month={May}, pages={2204–2210} }
 @article{koo_whangbo_dong_olejniczak_musfeldt_schlueter_geiser_1999, title={Analysis of polarized optical excitations by electronic band structure calculations: organic superconductor beta ''-(BEDT-TTF)(2)SF5CH2CF2SO3}, volume={112}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(99)00379-8}, abstractNote={The room temperature polarized optical conductivity of the superconducting salt β″-(BEDT-TTF)2SF5CH2CF2SO3 was analyzed by calculating its electronic band structure using the extended Hückel tight binding method. The electronic band structure obtained with double-zeta orbitals is consistent with the observed optical properties. The optical transitions in the energy region of 0–0.75 eV are intraband transitions associated with the bands that result from the highest-occupied molecular orbitals of the BEDT-TTF molecules. The optical conductivity is much stronger along the interstack direction (b-axis direction) than along the direction perpendicular to it throughout the energy region of 0–0.75 eV. This anisotropy is readily accounted for by the band dispersion relations calculated for the wave vector directions parallel to the b∗ and a∗ directions. Polarized optical conductivity provides indirect information about the anisotropy of band dispersion relations.}, number={7}, journal={SOLID STATE COMMUNICATIONS}, author={Koo, HJ and Whangbo, MH and Dong, J and Olejniczak, I and Musfeldt, JL and Schlueter, JA and Geiser, U}, year={1999}, pages={403–407} }
 @article{koo_whangbo_1999, title={Analysis of the spin-spin interactions in layered oxides alpha '-NaV2O5, CaV2O5 and MgV2O5 and the spin-Peierls distortion in alpha '-NaV2O5 by molecular orbital, Madelung energy and bond valence sum calculations}, volume={111}, ISSN={["1879-2766"]}, DOI={10.1016/S0038-1098(99)00179-9}, abstractNote={The spin–spin exchange parameters of α′-NaV2O5, CaV2O5 and MgV2O5 were examined by calculating the spin–spin interaction energies of their spin dimers, and the probable pairing distortion leading to the (2a×2b×4c) superstructure of α′-NaV2O5 was investigated by performing Madelung energy and bond valence sum analyses. In the V2O5 layers of α′-NaV2O5, CaV2O5 and MgV2O5, ladder chains of vanadium atoms are arranged in a staggered manner. CaV2O5 and MgV2O5 have an unpaired spin at each vanadium site, while α′-NaV2O5 has one unpaired spin in each rung of the ladder chains. The latter makes α′-NaV2O5 behave as a spin 1/2 Heisenberg linear chain system. Madelung energy and bond valence sum calculations for α′-NaV2O5 show that the pairing distortion from the uniform spin lattice to the zigzag spin lattice proposed by Seo and Fukuyama is energetically favorable. In the zigzag spin lattice the paired spins do not reside in the ladder chains but in between the ladder chains, which makes α′-NaV2O5 different from a simple spin-Peierls system.}, number={7}, journal={SOLID STATE COMMUNICATIONS}, author={Koo, HJ and Whangbo, MH}, year={1999}, pages={353–360} }
 @article{lee_koo_ren_whangbo_1999, title={Calculations and analysis of the electronic structures of transition-metal phosphosilicides Cu4SiP8, IrSi3P3, CoSi3P3, and FeSi4P4}, volume={147}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1999.8142}, abstractNote={Electronic structures of phosphosilicides Cu4SiP8, IrSi3P3, CoSi3P3, and FeSi4P4 were calculated using the extended Hückel tight-binding method and were analyzed in terms of a modified electron counting scheme. The d-block levels of these compounds appear well below the Fermi level, thereby indicating that the transition-metal atoms exist as d10 ions. Except for the case of IrSi3P3, the d-block energy levels of these compounds occur in a narrow energy window less than 1.5 eV wide. The Si 3p orbitals act as acceptor orbitals to the transition-metal d orbitals in IrSi3P3, CoSi3P3, and FeSi4P4.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Lee, KS and Koo, HJ and Ren, J and Whangbo, MH}, year={1999}, month={Oct}, pages={11–18} }
 @article{kelty_li_chen_chianelli_ren_whangbo_1999, title={Characterization of the RuS2(100) surface by scanning tunneling microscopy, atomic force microscopy, and near-edge X-ray absorption fine structure measurements and electronic band structure calculations}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp9842594}, abstractNote={The (100) surface of single-crystal RuS2 was characterized using atomic force microscopy (AFM), scanning tunneling microscopy (STM), near-ddge X-ray absorption fine structure (NEXAFS), and electronic band structure calculations. High-resolution STM and AFM images show that the as-cleaved RuS2(100) surface has a square lattice with the same cell parameters as does bulk RuS2, but the unit cell features are distinctly differently from those expected for the unreconstructed surface. Tunneling spectra reveal that significant surface states are present within the band gap of bulk RuS2. Comparison of the electron and fluorescence yield NEXAFS analysis of the RuS2(100) surface indicates that the surface Ru atoms are bonded only to S atoms and exist in a bulklike valence state. Some of the surface S atoms are passivated with bound oxygen atoms. On the basis of electronic band structure calculations, we propose a model for the reconstructed RuS2(100) surface consistent with the experimental observations.}, number={22}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Kelty, SP and Li, J and Chen, JG and Chianelli, RR and Ren, J and Whangbo, MH}, year={1999}, month={Jun}, pages={4649–4655} }
 @article{bar_brandsch_whangbo_1999, title={Correlation between frequency-sweep hysteresis and phase imaging instability in tapping mode atomic force microscopy}, volume={436}, ISSN={["1879-2758"]}, DOI={10.1016/S0039-6028(99)00702-5}, abstractNote={Abstract Frequency-sweep and phase imaging experiments of tapping mode atomic force microscopy were carried out for patterned self-assembled monolayers of S(CH 2 ) 15 CH 3 and S(CH 2 ) 12 OH groups on a polycrystalline Au substrate. The phase shift values of opposite signs associated with phase imaging instability are shown to be the same as the corresponding ones resulting from frequency-sweep hysteresis.}, number={1-3}, journal={SURFACE SCIENCE}, author={Bar, G and Brandsch, R and Whangbo, MH}, year={1999}, month={Aug}, pages={L715–L723} }
 @article{schmidt_thiele_whangbo_1999, title={Determination of the Se atom distribution in the layered compound Nb-3(Se1-xIx)I-7 by scanning tunneling microscopy}, DOI={10.1002/(sici)1099-0682(199905)1999:5<785::aid-ejic785>3.0.co;2-e}, abstractNote={The layered compound Nb3(Se1–xIx)I7 is obtained when the I atoms at the face-capping sites of the layered compound Nb3I8 are replaced by Se atoms. The amount and distribution of the Se atoms in Nb3(Se1–xIx)I7 were examined by scanning tunneling microscopy. The analysis shows that the distribution of the Se atoms is completely random.}, number={5}, journal={European Journal of Inorganic Chemistry}, author={Schmidt, P. J. and Thiele, G. and Whangbo, M. H.}, year={1999}, pages={785–787} }
 @article{schmidt_thiele_cantow_ren_whangbo_1999, title={Distribution of the Se atoms in the layered compound Nb-3(Se1-xIx)I-7 studied by scanning tunneling microscopy and electronic structure calculations}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp9843813}, abstractNote={The layered compound Nb3(Se1-xIx)I7 is obtained when the I atoms at the face-capping sites of Nb3I8 are substituted with Se atoms such that each Nb3(Se1-xIx)I7 layer is composed of Nb3I13 and Nb3SeI12 clusters. The amount and distribution of the Se atoms in Nb3(Se1-xIx)I7 were examined by carrying out scanning tunneling microscopy (STM) experiments for Nb3(Se1-xIx)I7. The reason the Nb3I13 and Nb3SeI12 clusters appear with different contrasts in the STM images Nb3(Se1-xIx)I7 was investigated by calculating partial density plots for ordered model layers [Nb3(Se1/3I2/3)I7]3 and (Nb3I8)3. In the STM images of Nb3(Se1-xIx)I7, the Nb3I13 and Nb3SeI12 clusters are distinguished because they undergo different extents of tip-force induced depression. Our analysis shows that the distribution of the Se atoms in Nb3Se1-xI7+x is random.}, number={18}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Schmidt, PJ and Thiele, G and Cantow, HJ and Ren, JQ and Whangbo, MH}, year={1999}, month={May}, pages={3626–3633} }
 @misc{bar_brandsch_whangbo_1999, title={Effect of tip sharpness on the relative contributions of attractive and repulsive forces in the phase imaging of tapping mode atomic force microscopy}, volume={422}, ISSN={["0039-6028"]}, DOI={10.1016/s0039-6028(98)00899-1}, abstractNote={The way in which the sharpness of a tip affects phase imaging in tapping mode atomic force microscopy was examined by performing experiments on polystyrene and Si surfaces with tips of different sharpness. The dominant tip–sample interaction controlling the cantilever vibration can be made repulsive with a sharp tip, and attractive with a dull tip. When the dominant interaction is either attractive or repulsive, the magnitude of the phase shift (Δφ) increases with decreasing set-point ratio rsp=Asp/A0, and the Δφ-vs.-rsp plots are nearly independent of the drive amplitude, A0. These observations indicate that the cantilever vibration is affected mainly by the amount of time the tip spends in going through the lower turning point of each oscillation and by the forces whose force derivatives change sharply during this period.}, number={1-3}, journal={SURFACE SCIENCE}, author={Bar, G and Brandsch, R and Whangbo, MH}, year={1999}, month={Feb}, pages={L192–L199} }
 @article{lee_koo_dai_ren_whangbo_1999, title={Electron counting scheme relevant for late transition metal compounds with weakly electronegative ligands. Electronic band structure study of phosphosilicides PtSi3P2 and NiSi2P3}, volume={38}, ISSN={["0020-1669"]}, DOI={10.1021/ic980761r}, abstractNote={The conventional electron counting scheme often leads to erroneous predictions for late transition metal compounds with weakly electronegative main group ligand atoms. The cause for this deficiency was analyzed, and a modified electron counting scheme was proposed for predicting the frontier orbitals of such compounds. The modified scheme predicts that the transition metal atoms of such compounds have a d10 electron count, and their frontier orbitals are represented by the highest-lying lone pair levels of the main group ligand atoms. These predictions were tested by carrying out electronic band structure calculations for phosphosilicides PtSi3P2 and NiSi2P3. The relevance of nonstoichiometric compositions of these phases was also discussed.}, number={2}, journal={INORGANIC CHEMISTRY}, author={Lee, KS and Koo, HJ and Dai, D and Ren, J and Whangbo, MH}, year={1999}, month={Jan}, pages={340–345} }
 @article{stagarescu_duda_smith_seo_whangbo_jerome_haddon_brooks_guo_nordgren_1999, title={Electronic structure of the organic conductors kappa-ET2Cu(SCN)(2) and kappa-ET2Cu[N(CN)(2)]Br studied using soft X-ray absorption and soft X-ray emission}, volume={143}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1998.8046}, abstractNote={Abstract The problem of resolving molecular components of the electronic structure of complex, organic solids with respect to their chemical and orbital character has been approached using core-level photon spectroscopies. Specifically, the bulk C 2poccupied and unoccupied partial densities of states (PDOS) of the organic superconductorsκ-ET2Cu(SCN)2andκ-ET2Cu[N(CN)2]Br were measured using a combination of high-resolution soft X-ray absorption (SXA) and soft X-ray emission (SXE). The PDOS was also calculated using a tight binding model, and the measured spectra compared directly to that predicted by the calculations. The emission and absorption spectra from both materials were found to be quite similar, reflecting mostly contributions from the common conductive ET layers. The presence of two nonequivalent carbon sites of the ET molecule was identified in the SXA spectra. Contributions from theπandσstates were identified in the emission spectra. The occupied C 2pbandwidth was found to be approximately 17eV. An observed dependence of the SXE spectra on the excitation energy is partly accounted for by a simple model that considers the presence of the two nonequivalent ET carbon sites. We also find evidence in the SXE spectra for a high degree of localization in the lowest unoccupied states.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Stagarescu, CB and Duda, LC and Smith, KE and Seo, DK and Whangbo, MH and Jerome, D and Haddon, RC and Brooks, JS and Guo, JH and Nordgren, J}, year={1999}, month={Feb}, pages={1–8} }
 @article{whangbo_bengel_jobic_brec_1999, title={Flexibility of the MPS4- chains of the KMPS4 (M = Ni, Pd) compounds studied by molecular orbital calculations and atomic force microscopy measurements}, volume={147}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1999.8245}, abstractNote={The flexibility of the MPS−4 chains of KMPS4 (M=Ni, Pd) was examined by performing contact mode atomic force microscopy (AFM) measurements for the (001) surface of KNiPS4 and also by performing extended Hückel tight binding calculations for the [M(PS4)2]4− entities of KMPS4. The observed AFM images were analyzed by calculating the total electron density plots for an isolated [NiPS4]− slab of the (001) surface. Our calculations show that the PS3−4 ions are more strongly bound to the Pd2+ ions in KPdPS4 than to the Ni2+ ions in KNiPS4, and that the bonding between the PS3−4 anions and M2+ (M=Ni, Pd) cations is flexible with respect to the rotational motions of the PS3−4 anions. The AFM images recorded for the (001) surface of KNiPS4 indicate that the PS3−4 anions on the surface undergo a rotational relaxation when the scanning tip passes by.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Whangbo, MH and Bengel, H and Jobic, S and Brec, R}, year={1999}, month={Oct}, pages={235–239} }
 @article{zhu_long_musfeldt_wei_sarrao_fisk_negishi_inoue_koo_whangbo_1999, title={High field optical response of eta-Mo4O11}, volume={9}, ISSN={["1155-4339"]}, DOI={10.1051/jp4:19991063}, number={P10}, journal={JOURNAL DE PHYSIQUE IV}, author={Zhu, Z and Long, VC and Musfeldt, JL and Wei, X and Sarrao, J and Fisk, Z and Negishi, H and Inoue, M and Koo, HJ and Whangbo, MH}, year={1999}, month={Dec}, pages={251–253} }
 @article{bar_delineau_brandsch_bruch_whangbo_1999, title={Importance of the indentation depth in tapping-mode atomic force microscopy study of compliant materials}, volume={75}, ISSN={["0003-6951"]}, DOI={10.1063/1.125581}, abstractNote={We studied the response of a cantilever tapping on polydimethylsiloxane (PDMS) samples of different crosslink density. It is shown experimentally that the tip deeply penetrates into the compliant PDMS samples. A more compliant material leads to a larger indentation such that at a given set-point ratio the indentation force is nearly constant on samples of different elastic moduli. This confirms the simulations by J. Tamayo and R. Garcia [Appl. Phys. Lett. 71, 2394 (1997)] that phase contrast acquired at constant set point does not depend on the sample’s modulus if other contrast relevant parameters remain identical. PDMS samples of different crosslink density are distinguished in terms of amplitude and phase versus distance measurements if the tip-sample interaction is made substantially large and indentation is taken into account.}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Bar, G and Delineau, L and Brandsch, R and Bruch, M and Whangbo, MH}, year={1999}, month={Dec}, pages={4198–4200} }
 @article{wang_vanzile_schlueter_geiser_kini_sche_koo_whangbo_nixon_winter_et al._1999, title={In-plane ESR microwave conductivity measurements and electronic band structure studies of the organic superconductor beta ''-(BEDT-TTF)(2)SF5CH2CF2SO3}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp991268j}, abstractNote={The electronic structure of the organic superconductor {beta}''-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} (BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene) was characterized with the use of electron spin resonance (ESR) spectroscopy and electronic band structure calculations. The room-temperature ESR line width is 24-27 G in the plane of a donor molecule layer (i.e., in the ab-plane) and {approx}32 G along the normal to this plane (i.e., along the c*-direction). The ab-plane anisotropy of the microwave conductivity was extracted for the first time from the ESR Dysonian line shape analysis. The in-plane conductivity varies sinusoidally, is maximal along the interstack direction (b-axis), and is minimal along the donor stack direction (a-axis). The Fermi surfaces of the title compound consist of a 2D hole pocket and a pair of 1D wavy lines. The directions for the in-plane conductivity maximum and minimum are in excellent agreement with the electronic band structure calculated for {beta}''-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}, and the origin of the in-plane conductivity anisotropy lies in the one-dimensional part of the Fermi surface. This is the first time that an organic conductor shows Dysonian ESR line shape due to its 2D and strongly metallic nature, yet the 1D character is revealed simultaneously through themore » in-plane conductivity anisotropy.« less}, number={26}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Wang, HH and VanZile, ML and Schlueter, JA and Geiser, U and Kini, AM and Sche, PP and Koo, HJ and Whangbo, MH and Nixon, PG and Winter, RW and et al.}, year={1999}, month={Jul}, pages={5493–5499} }
 @article{stagarescu_duda_smith_seo_whangbo_jerome_haddon_brooks_guo_nordgren_1999, title={Molecular components of the bulk electronic structure of organic conductors: A soft X-ray absorption and soft X-ray emission spectroscopy approach}, volume={101}, ISSN={["0368-2048"]}, DOI={10.1016/S0368-2048(98)00346-6}, abstractNote={Abstract The problem of resolving molecular components of the electronic structure of complex, organic solids with respect to their chemical and orbital character has been approached using soft X-ray absorption (SXA) and soft X-ray emission (SXE) spectroscopy. These techniques are powerful probes of the site and angular-momentum resolved partial density of states (PDOS) for both occupied and unoccupied states. Therefore these spectroscopies are particularly suited for an analysis of the density of states of multi-atomic, complex materials as the ET-based organic conductors, allowing site-specific electronic structure to be measured. We present a preliminary picture of the electronic structure of κ-ET 2 Cu(SCN) 2 and κ-ET 2 Cu[N(CN) 2 ]Br as measured by SXE and SXA performed at the C1s and N1s core levels.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Stagarescu, CB and Duda, LC and Smith, KE and Seo, DK and Whangbo, MH and Jerome, D and Haddon, RC and Brooks, JS and Guo, JH and Nordgren, J}, year={1999}, month={Jun}, pages={539–544} }
 @article{long_zhu_musfeldt_wei_koo_whangbo_jegoudez_revcolevschi_1999, title={Polarized optical reflectance and electronic band structure of alpha '-NaV2O5}, volume={60}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.60.15721}, abstractNote={We report polarized optical reflectance studies of ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{NaV}}_{2}{\mathrm{O}}_{5}$ between 0.5 and 6 eV as a function of temperature (T) and magnetic field $(H).$ The electronic excitations and their polarization dependence are interpreted according to our extended H\"uckel tight-binding polarized band structure calculations. Strong bands near 1 eV in both chain and rung directions are attributed to V $\stackrel{\ensuremath{\rightarrow}}{d}d$ transitions. Charge transfer excitations are estimated to begin near 3.3 eV and have significant strength at 4.4 eV and above. The reflectance ratios, $\ensuremath{\Delta}R(T)=R(T)/R(T=4 \mathrm{K}),$ measured at $H=0$ and 28 T, reveal broad polarization-dependent changes through the low temperature transition, ${T}_{c}.$ Integrated intensities of $\ensuremath{\Delta}R$ features exhibit a second-order transition at 36 K in zero field and at $33\ifmmode\pm\else\textpm\fi{}1 \mathrm{K}$ in high field, consistent with a spin-Peierls aspect to the phase transition.}, number={23}, journal={PHYSICAL REVIEW B}, author={Long, VC and Zhu, Z and Musfeldt, JL and Wei, X and Koo, HJ and Whangbo, MH and Jegoudez, J and Revcolevschi, A}, year={1999}, month={Dec}, pages={15721–15727} }
 @article{lee_koo_whangbo_1999, title={Spin-spin interactions in the oxides A(3)M ' MO6 (M = Rh, Ir; A = Ca, Sr; M ' = alkaline earth, Zn, Cd, Na) of the K4CdCl6 structure type examined by electronic structure calculations}, volume={38}, ISSN={["0020-1669"]}, DOI={10.1021/ic9813819}, abstractNote={The oxides A(3)M'MO(6) (M = Rh, Ir; A = Ca, Sr; M' = alkaline earth, Zn, Cd) of the K(4)CdCl(6) structure type consist of isolated (MO(6))(8)(-) octahedral anions and exhibit an antiferromagnetic ordering at low temperatures. The spin-spin interactions in these oxides, Ca(3)NaMO(6) (M = Ir, Ru), and Sr(3)NaRuO(6) were examined by calculating how strongly the t(2g)-block levels of adjacent (MO(6))((6+)(n)()())(-) (n = 1, 2) anions interact in the presence and absence of the intervening cations A(2+) and M' (n)()(+) (n = 1, 2). Our calculations show that the spin-spin interactions in these oxides are three-dimensional, and the superexchange interactions occur mainly through the short intrachain and interchain M-O.O-M linkages. When the M(n)()(+) cation is very small compared with the A(2+) cation, the intrachain interaction is substantially stronger than the interchain interaction. The opposite is found when the sizes of the M(n)()(+) and A(2+) cations become similar.}, number={9}, journal={INORGANIC CHEMISTRY}, author={Lee, KS and Koo, HJ and Whangbo, MH}, year={1999}, month={May}, pages={2199–2203} }
 @article{beckmann_wanka_wosnitza_schlueter_williams_nixon_winter_gard_ren_whangbo_1998, title={Characterization of the Fermi surface of the organic superconductor beta ''-(ET)(2)SF5CH2CF2SO3 by measurements of Shubnikov-de Haas and angle-dependent magnetoresistance oscillations and by electronic band-structure calculations}, volume={1}, ISSN={["1434-6028"]}, DOI={10.1007/s100510050185}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL B}, author={Beckmann, D and Wanka, S and Wosnitza, J and Schlueter, JA and Williams, JM and Nixon, PG and Winter, RW and Gard, GL and Ren, J and Whangbo, MH}, year={1998}, month={Feb}, pages={295–300} }
 @article{bar_thomann_whangbo_1998, title={Characterization of the morphologies and nanostructures of blends of poly(styrene) block-poly(ethene-co-but-1-ene)-block-poly(styrene) with isotactic and atactic polypropylenes by tapping-mode atomic force microscopy}, volume={14}, ISSN={["0743-7463"]}, DOI={10.1021/la9711544}, abstractNote={Blends of poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) (SEBS) with isotactic polypropylene (i-PP) and with atactic polypropylene (a-PP) were prepared under different thermal treatments. On the basis of the phase imaging of tapping-mode atomic force microscopy (TMAFM), we investigated the nanostructures and the morphologies of these blends as well as their dependence on blending history. The observed macrophase separation in i-PP/SEBS blends is caused by the incompatibility of the two polymer components. The microphase separation of the SEBS component depends on the thermal treatment. The morphology of a-PP/SEBS blends exhibits domains that span a wide range of sizes from 15 μm down to 15 nm. Our work shows that TMAFM phase imaging is an important and competitive tool for studying the microphase separation of polymers.}, number={5}, journal={LANGMUIR}, author={Bar, G and Thomann, Y and Whangbo, MH}, year={1998}, month={Mar}, pages={1219–1226} }
 @article{zhang_warren_haushalter_clearfield_seo_whangbo_1998, title={Comparative study of the structural, electronic, and magnetic properties of the layered ternary vanadium oxides CaV4O9, Cs2V4O9, and [H2N(CH2)(4)NH2]V4O9}, volume={10}, ISSN={["0897-4756"]}, DOI={10.1021/cm970653n}, abstractNote={We report the preparation, single-crystal X-ray structure determination, and magnetic susceptibility measurements of a new ternary vanadium oxide, [H2N(CH2)4NH2]V4O9. This compound has isolated V4O92- layers made up of edge-sharing VO5 square pyramids. The V4O92- layers of [H2N(CH2)4NH2]V4O9 ([H2N(CH2)4NH2] = piperidinium) differ from those of two other ternary vanadium oxides, CaV4O9 and A2V4O9 (A = Rb, Cs), in the way the VO5 square pyramids are shared, and the magnetic susceptibilities of the three oxides are widely different in their maximum susceptibility values and the temperatures where these values occur. To explain these observations, the electronic structures of the three oxides were analyzed based on molecular orbital calculations.}, number={4}, journal={CHEMISTRY OF MATERIALS}, author={Zhang, YP and Warren, CJ and Haushalter, RC and Clearfield, A and Seo, DK and Whangbo, MH}, year={1998}, month={Apr}, pages={1059–1064} }
 @article{dai_li_ren_whangbo_1998, title={Description of ligand field splitting in terms of density functional theory: Calculations of the split levels of the F-2(5/2) and F-2(7/2) subterms in CeO and CeF under the weak field coupling scheme}, volume={108}, ISSN={["1089-7690"]}, DOI={10.1063/1.475747}, abstractNote={A new method of calculating the split levels of the spectroscopic subterms of lanthanide ions under the weak field coupling scheme was formulated based on the density functional theory (DFT) and ligand field theory. To construct the ligand field potential acting on the 4f electrons of a lanthanide compound, the potential of the molecule was obtained by DFT calculations, the 4f-electron contributions to the potential were removed, and the pseudopotentials of the ligands were added to include the Pauli repulsion between the 4f electrons and ligand electrons. The ligand field potential thus obtained includes the effects of the metal-ligand overlap and covalency on ligand-field splitting. This method was tested by calculating the split levels of the 2F5/2 and 2F7/2 subterms associated with the 4f16s1 and 4f16s2 configurations of CeO and CeF, respectively. Our results are in excellent agreement with experiment and indicate that the split levels of lanthanide compounds can be calculated accurately using our method.}, number={9}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Dai, DD and Li, LM and Ren, J and Whangbo, MH}, year={1998}, month={Mar}, pages={3479–3488} }
 @article{ren_whangbo_dai_li_1998, title={Description of ligand field splitting in terms of density functional theory: Split levels of the lowest-lying subterms of the 4f(n-1)6s(2) (n=3-14) configurations in lanthanide monofluorides LnF (Ln=Pr-Yb)}, volume={108}, ISSN={["0021-9606"]}, DOI={10.1063/1.476276}, abstractNote={The split levels associated with the lowest-lying subterms of the 4fn−16s2 (n=3–14) configurations of lanthanide monofluorides LnF (Ln=Pr–Yb) were calculated by employing the combined ligand field and density functional theory (CLDT) method recently proposed. The 288 calculated split levels are in excellent agreement with experiment and hence shows that the CLDT method can accurately reproduce the low-lying electronic excited states of lanthanide compounds. To quantitatively describe the low-lying electronic states of a lanthanide compound, therefore, the effective ligand potential must include the Coulomb and exchange-correlation potentials of the compound as well as the pseudopotentials of the ligands.}, number={20}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Ren, J and Whangbo, MH and Dai, DD and Li, LM}, year={1998}, month={May}, pages={8479–8484} }
 @misc{whangbo_bar_brandsch_1998, title={Description of phase imaging in tapping mode atomic force microscopy by harmonic approximation}, volume={411}, ISSN={["0039-6028"]}, DOI={10.1016/s0039-6028(98)00349-5}, abstractNote={Tapping mode atomic force microscopy measurements were performed for an elastomer, polydimethylsiloxane, to obtain amplitudes and phase angles as a function of driving frequency at various driving and set-point amplitudes. The amplitude curves support the harmonic approximation that the vibrational characteristics of a tapping cantilever are essentially harmonic. Based on this approximation, we derived simple analytical formulas describing the phase shift, the predictions of which agree reasonably well with experiment. Our work shows that the phase shift is influenced by the dissipation energy as well as the resonance frequency shift associated with the tip–sample interaction, and suggests a simple way of estimating the dissipation energy.}, number={1-2}, journal={SURFACE SCIENCE}, author={Whangbo, MH and Bar, G and Brandsch, R}, year={1998}, month={Aug}, pages={L794–L801} }
 @misc{bar_brandsch_whangbo_1998, title={Description of the frequency dependence of the amplitude and phase angle of a silicon cantilever tapping on a silicon substrate by the harmonic approximation}, volume={411}, ISSN={["0039-6028"]}, DOI={10.1016/s0039-6028(98)00348-3}, abstractNote={The frequency dependence of the amplitude and phase angle of a silicon cantilever tapping on a silicon surface was examined. The amplitude and phase angle curves exhibit hysteresis depending on the driving and set-point amplitudes. The main features of these curves are explained in terms of the harmonic approximation. The frequency shifts determined from the phase curves vary almost linearly as a function of the set-point ratio, in support of the harmonic approximation. The quality factor of a tapping cantilever was estimated from amplitude and phase curves using the harmonic approximation. The quality factor is reduced by the tip–sample interaction, and this reduction is stronger when the interaction is dominated by repulsive forces than by attractive forces.}, number={1-2}, journal={SURFACE SCIENCE}, author={Bar, G and Brandsch, R and Whangbo, MH}, year={1998}, month={Aug}, pages={L802–L809} }
 @misc{bar_brandsch_whangbo_1998, title={Effect of viscoelastic properties of polymers on the phase shift in tapping mode atomic force microscopy}, volume={14}, ISSN={["0743-7463"]}, DOI={10.1021/la980969p}, abstractNote={On the basis of the frequency-sweep tapping mode atomic force microscopy (TMAFM) experiments for polystyrene (PS) and poly(dimethylsiloxane) (PDMS), the validity of the harmonic approximation for describing the phase shift of TMAFM was tested by evaluating the analytical expressions derived from the approximation. Our study shows that the phase shift is almost quantitatively described by the harmonic approximation. By analyzing the results of these experiments, it was also examined how the viscoelastic properties of a polymer affect the nature of the tip−sample interaction. The nature of the tip−sample interaction is strongly affected by the sharpness of the tip and by the elasticity, viscosity, and plasticity of a polymer sample. On a strongly glassy, brittle sample with a low impact strength, such as PS, the phase shift can be dominated by the attractive force with the use of a dull tip, while on a strongly elastic sample, such as PDMS, the phase shift can be dominated by the indentation force with the use of a sharp tip.}, number={26}, journal={LANGMUIR}, author={Bar, G and Brandsch, R and Whangbo, MH}, year={1998}, month={Dec}, pages={7343–7348} }
 @article{thomann_cantow_bar_whangbo_1998, title={Investigation of morphologies and nanostructures of polymer blends by tapping mode phase imaging}, volume={66}, ISSN={["0947-8396"]}, DOI={10.1007/s003390051333}, journal={APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING}, author={Thomann, Y and Cantow, HJ and Bar, G and Whangbo, MH}, year={1998}, month={Mar}, pages={S1233–S1236} }
 @article{koo_whangbo_mccarroll_greenblatt_gautier_halet_gougeon_1998, title={On the origin of the anomalous electrical resistivity of LnMo(5)O(8) (Ln = trivalent rare earth)}, volume={108}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(98)00407-4}, abstractNote={Electronic structures of AMo5O8 (A=rare earth, alkaline earth) and the solid solution Sr1−xLaxMo5O8 (x=0–1) were examined using the extended Hückel tight binding method. AMo5O8 phases with divalent A cations (A=Sr, Ca, Eu) are normal semiconductors with small band gap. The Fermi surfaces of Sr1−xLaxMo5O8 (0.0<x≤1.0) and LnMo5O8 (Ln=trivalent rare earth) do not exhibit any nesting. In the electronic structures of LnMo5O8 (Ln=trivalent rare earth) phases, the Fermi level is dominated by the d-orbitals of the Mo(2) atoms of their Mo10 clusters. With decreasing x from 1.0 in Sr1−xLaxMo5O8, the dominance of the Mo(2) atoms at the Fermi level sharply diminishes. Based on this observation, we proposed a probable reason for the weakly semiconducting state above 180 K and the metallic state below 180 K in LnMo5O8 (Ln=trivalent rare earth).}, number={8}, journal={SOLID STATE COMMUNICATIONS}, author={Koo, HJ and Whangbo, MH and McCarroll, WH and Greenblatt, M and Gautier, R and Halet, JF and Gougeon, P}, year={1998}, pages={539–544} }
 @article{seo_gupta_whangbo_hillebrecht_thiele_1998, title={Pressure-induced changes in the structure and band gap of CsGeX3 (X = Cl, Br) studied by electronic band structure calculations}, volume={37}, ISSN={["0020-1669"]}, DOI={10.1021/ic970659e}, abstractNote={Tight-binding electronic band structures of cesium trihalometalates CsGeX3 (X = Cl, Br) were calculated to examine the pressure-dependence of their crystal structures and band gaps as well as their primitive cubic to rhombohedral structural phase transitions. In agreement with experiment, our calculations show that an increase in the applied pressure decreases the band gap and the stability of CsGeX3, and the band gap is larger for CsGeCl3 than for CsGeBr3. CsGeCl3 has a much stronger second-order Jahn−Teller instability than does CsGeBr3 and therefore can adopt a disordered cubic phase unlike CsGeBr3.}, number={3}, journal={INORGANIC CHEMISTRY}, author={Seo, DK and Gupta, N and Whangbo, MH and Hillebrecht, H and Thiele, G}, year={1998}, month={Feb}, pages={407–410} }
 @article{whangbo_bar_brandsch_1998, title={Qualitative relationships describing height and phase images of tapping mode atomic force microscopy. An application to micro-contact-printed patterned self-assembled monolayers}, volume={66}, ISSN={["1432-0630"]}, DOI={10.1007/s003390051340}, journal={APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING}, author={Whangbo, MH and Bar, G and Brandsch, R}, year={1998}, month={Mar}, pages={S1267–S1270} }
 @article{bengel_jobic_deudon_rouxel_seo_whangbo_1998, title={Scanning tunneling and atomic force microscopy study of the misfit layer compounds (LaS)(1.14)(NbS2)(n) (n=1,2) and [(Pb,Sb)S)](1.14)NbS2}, volume={400}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(97)00882-0}, abstractNote={The misfit layer compounds (LaS)1.14(NbS2)n (n=1, 2) and [(Pb,Sb)S]1.14NbS2 were examined by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). In these compounds the NaCl-type double MS (M=La, Pb, Sb) layers (Q layers) alternate with the NbS2 layers (H layers) made up of NbS6 trigonal prisms. It was possible to record AFM and STM images for only the H layers for (LaS)1.14(NbS2)n, but for both the H- and Q-layers for [(Pb,Sb)S]1.14NbS2. Partial and total electron density plots of the H and Q layers were calculated to interpret the observed STM and AFM images. The bright spots in the STM and AFM images of the H layer correspond to S atoms, and those of the Q layer to Pb and Sb atoms. The STM images for the Q layers of [(Pb,Sb)S]1.14NbS2 suggest that a short-range ordering of the Pb and Sb atoms occurs in the (Pb,Sb)S sheets of the Q layer.}, number={1-3}, journal={SURFACE SCIENCE}, author={Bengel, H and Jobic, S and Deudon, C and Rouxel, J and Seo, DK and Whangbo, MH}, year={1998}, month={Mar}, pages={266–276} }
 @article{koo_whangbo_kennedy_1998, title={Similarities and differences in the structural and electronic properties of ruthenium and iridium pyrochlores A(2)M(2)O(7-y) (M = Ru, Ir)}, volume={136}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1997.7705}, abstractNote={Electronic band structures of the ruthenium and iridium pyrochloresA2M2O6O′1−y(M=Ru, Ir) were examined using the extended Hückel tight-binding method. The metal versus semiconductor behaviors of these pyrochlores are explained in terms of the Mott–Hubbard localization concept. TheM–O,A–O, andA–O′ distances andM–O–Mangles ofA2M2O6O′1−y(M=Ru, Ir) were analyzed in terms of theAcation ionic radius. TheM–O distance and theM–O–Mangle are strongly influenced by the overlap repulsion between the filled shells of theAcation and O2−anions. The O′ vacancies of the pyrochloresA2M2O6O′1−ywith polarizableAcations such as Tl+, Pb2+, or Bi3+occur most likely to reduce the overlap repulsion associated with the 6sorbitals of theAcations.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Koo, HJ and Whangbo, MH and Kennedy, BJ}, year={1998}, month={Mar}, pages={269–273} }
 @article{ogawa_irie_isoda_kobayashi_whangbo_1998, title={Simulation of long-range contrast modulation in scanning tunneling microscope image of perylene-3,4,9,10-tetracarboxylic-dianhydride monolayer on graphite}, volume={37}, ISSN={["0021-4922"]}, DOI={10.1143/JJAP.37.3864}, abstractNote={In order to simulate the scanning tunneling microscope (STM) image of perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) on graphite, we calculated the partial electron density, which is proportional to the tunneling current, by the extended Hückel tight binding method. The typical STM images of PTCDA have two characteristic features: (i) long-range contrast modulation caused by point-on-line coincidence and (ii) contrast difference due to molecular orientation with respect to the graphite substrate. Using the present simulation, these features can be reproduced from the expected geometrical relationship between PTCDA and graphite.}, number={6B}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS}, author={Ogawa, T and Irie, S and Isoda, S and Kobayashi, T and Whangbo, MH}, year={1998}, month={Jun}, pages={3864–3866} }
 @article{jung_seo_ren_whangbo_1998, title={Simulation of the scanning tunneling and atomic force microscopy images of a xanthine monolayer on graphite}, volume={401}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(98)00069-7}, abstractNote={The atomic force microscopy (AFM) and scanning tunneling microscopy (STM) images of a monolayer of xanthine molecules adsorbed on graphite were simulated by calculating total and partial electron density plots for a model bilayer of xanthine and graphite. Unlike the case of the total density plots, the partial electron density plots depend strongly on the registry of xanthine molecules on the graphite lattice. This result explains why the STM images show a superstructure modulation, whereas the AFM images do not.}, number={3}, journal={SURFACE SCIENCE}, author={Jung, D and Seo, DK and Ren, J and Whangbo, MH}, year={1998}, month={Apr}, pages={476–481} }
 @article{seo_whangbo_neininger_thiele_1998, title={Single-crystal X-ray diffraction and electronic band structure studies of PdTeI}, volume={137}, ISSN={["1095-726X"]}, DOI={10.1006/jssc.1997.7669}, abstractNote={The crystal structure of PdTeI was determined by single-crystal X-ray diffraction measurements, and its electronic band structure was calculated using the extended-Hückel tight-binding method. Each Pd3+(d7) cation of PdTeI is located at a distorted octahedral site, so that PdTeI has four half-filledz2bands dispersive mainly along thecdirection. Thus, optical and transport properties of PdTeI are predicted to be highly one-dimensional, although the crystal structure of PdTeI is three-dimensional. Implications of the crystal and electronic structures on the physical properties of PdTeI are discussed.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Seo, DK and Whangbo, MH and Neininger, K and Thiele, G}, year={1998}, month={May}, pages={206–210} }
 @article{wang_haushalter_whangbo_1998, title={Synthesis, characterization, and electronic structure analysis of (Et4N)(4)KAuAs4Te8 and electron counting for the zintl anion containing a square-planar AuTe4 unit}, volume={37}, ISSN={["0020-1669"]}, DOI={10.1021/ic980389f}, abstractNote={The structure of (Et4N)4KAuAs4Te8 consists of two different cations and an AuAs4Te85- anion. The AuAs4Te85- anion can be considered in terms of two As2Te44- anions coordinating to a Au3+ cation to form a square-planar AuTe4 unit. However, molecular orbital calculations show that the Au cations of the square-planar AuTe4 units in (Et4N)4KAuAs4Te8 and other compounds are best described to be monovalent Au+. Electron-counting problems for the square-planar AuTe4 unit and its isostructural analogue TeTe4 unit are discussed.}, number={23}, journal={INORGANIC CHEMISTRY}, author={Wang, C and Haushalter, RC and Whangbo, MH}, year={1998}, month={Nov}, pages={6096–6099} }
 @article{kuo_skove_verebelyi_li_mackay_hwu_whangbo_brill_1998, title={Unusual physical properties of KCu7-xS4 at diffusive one-dimensional ordering transitions}, volume={57}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.57.3315}, abstractNote={Single crystals of quasi-one-dimensional sulfides ${\mathrm{KCu}}_{7\ensuremath{-}x}{\mathrm{S}}_{4}$ with $x=0.00,0.12$, and 0.34 were prepared by electrochemical methods. Temperature-dependent properties of resistance, thermal conductivity, thermoelectric power, and heat capacity ${C}_{P}$ were studied on single-crystal samples. These measurements show several anomalies which we associate with phase transitions, with the transition temperatures and physical properties depending strongly on $x$. Most interestingly, measurements of ${C}_{P}$ with an ac technique show very unusual hysteresis and frequency dependence. The present work indicates that these phase transitions are due to vacancy ordering involving ${\mathrm{Cu}}^{+}$-ion diffusion along the Cu(2)-Cu(2) zigzag chains.}, number={6}, journal={PHYSICAL REVIEW B}, author={Kuo, YK and Skove, MJ and Verebelyi, DT and Li, H and Mackay, R and Hwu, SJ and Whangbo, MH and Brill, JW}, year={1998}, month={Feb}, pages={3315–3325} }
 @article{hess_schlenker_dumas_greenblatt_canadell_whangbo_1997, title={Anisotropic thermopower in the charge density wave quasi two-dimensional compounds (PO2)(4)(WO3)(2m)(m=4, 6)}, volume={86}, ISSN={["0379-6779"]}, DOI={10.1016/S0379-6779(97)81090-9}, abstractNote={Abstract Thermopower and Hall effect have been measured between 4.2 K and 300 K on the monophosphate tungsten bronzes (PO 2 ) 4 (WO 3 ) 2m with m=4 and 6. The Peierls transitions can be clearly observed. In the normal state, both compounds behave as nearly compensated metals in agreement with band structure calculations. The anisotropic thermopower found in the charge density wave state of the m=6 compound gives information on the carrier pockets left by the gap openings along different crystallographic directions.}, number={1-3}, journal={SYNTHETIC METALS}, author={Hess, C and Schlenker, C and Dumas, J and Greenblatt, M and Canadell, E and Whangbo, MH}, year={1997}, month={Feb}, pages={2189–2190} }
 @article{wang_fox_yagubskii_kushch_kotov_whangbo_1997, title={Direct observation of the electron-donating property of the 5,6-dihydro-1,4-dithiin-2,3-dithiolate (dddt) ligands in square planar M(dddt)(2) complexes (M=Ni, Pd, Pt, and Au)}, volume={119}, ISSN={["0002-7863"]}, DOI={10.1021/ja9704747}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDirect Observation of the Electron-Donating Property of the 5,6-Dihydro-1,4-dithiin-2,3-dithiolate (dddt) Ligands in Square Planar M(dddt)2 Complexes (M = Ni, Pd, Pt, and Au)H. Hau Wang, Shannon B. Fox, Eduard B. Yagubskii, Lyudmila A. Kushch, Alexander I. Kotov, and Myung-Hwan WhangboView Author Information Chemistry and Materials Science Divisions Argonne National Laboratory Argonne, Illinois 60439 Institute of Chemical Physics in Chernogolovka Russian Academy of Sciences Chernogolovka MD, 142432 Russia Department of Chemistry North Carolina State University Raleigh, North Carolina 27695-8204 Cite this: J. Am. Chem. Soc. 1997, 119, 32, 7601–7602Publication Date (Web):August 13, 1997Publication History Received12 February 1997Published online13 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ja9704747Copyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views236Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (103 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Gold,Ligands,Palladium,Platinum,Salts Get e-Alerts}, number={32}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Wang, HH and Fox, SB and Yagubskii, EB and Kushch, LA and Kotov, AI and Whangbo, MH}, year={1997}, month={Aug}, pages={7601–7602} }
 @article{seo_whangbo_subramanian_1997, title={Electronic band structure study of colossal magnetoresistance in Tl2Mn2O7}, volume={101}, ISSN={["1879-2766"]}, DOI={10.1016/S0038-1098(96)00622-9}, abstractNote={The electronic structure of Tl2Mn2O7 was examined by performing tight binding band calculations. The overlap between the Mnt2g- and Tl 6s-block bands results in a partial filling of the Tl 6s-block bands. The associated Fermi surface consists of 12 cigar-shape electron pockets with each electron pocket about 11000 of the first Brillouin zone in size. The Tl 6s-block bands have orbital contributions from the Mn atoms, and the carrier density is very low. These are important for the occurrence of a colossal magnetoresistance in Tl2Mn2O7.}, number={6}, journal={SOLID STATE COMMUNICATIONS}, author={Seo, DK and Whangbo, MH and Subramanian, MA}, year={1997}, month={Feb}, pages={417–421} }
 @article{lee_seo_whangbo_1997, title={Electronic band structure study of the anomalous electrical and superconducting properties of hexagonal alkali tungsten bronzes A(x)WO(3) (A=K, Rb, Cs)}, volume={119}, ISSN={["0002-7863"]}, DOI={10.1021/ja964455t}, abstractNote={The electrical and superconducting properties of hexagonal alkali tungsten bronzes AxWO3 (A = K, Rb, Cs) were examined by calculating the electronic band structure of a representative hexagonal tungsten bronze and analyzing reported crystal structures of AxWO3 (A = K, Rb, Cs). These bronzes possess one-dimensional (1D) and three-dimensional Fermi surfaces. The metal-to-semiconductor-to-metal transitions and superlattice reflections in KxWO3 and RbxWO3 are explained by a charge density wave (CDW) associated with the 1D Fermi surface. There occurs a maximum in the plots of the CDW onset temperature TB versus x for KxWO3 and RbxWO3. The presence of this maximum and the absence of a CDW in CsxWO3 reflect the balance of two opposing energy factors, the electronic instability and lattice stiffness, in forming a CDW. The dependence of the superconducting transition temperature TC on x suggests that a CDW transition removes lattice phonons conducive for superconductivity.}, number={17}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Lee, KS and Seo, DK and Whangbo, MH}, year={1997}, month={Apr}, pages={4043–4049} }
 @article{seo_ren_whangbo_canadell_1997, title={Electronic band structure study of the transport properties of the intermetallic compounds ZrRuP and ZrRuSi}, volume={36}, ISSN={["0020-1669"]}, DOI={10.1021/ic970148s}, abstractNote={Electrical properties of the intermetallic superconductors h-ZrRuP, o-ZrRuP, and h-ZrRuSi were examined by calculating their electronic structures on the basis of the extended Hückel tight-binding method. To a first approximation, the electronic structure of ZrRuP is well described in terms of the oxidation state Zr(4+)(RuP)(4)(-). This picture provides simple explanations for why both h-ZrRuP and o-ZrRuP have low N(E(f)) values and why h-ZrRuP has a nearly half-filled one-dimensional (1D) band dispersive along the c direction. A charge density wave instability associated with such a 1D band probably causes a c-axis doubling structural distortion in h-HfRuAs and h-TiRuAs. We discussed probable reasons for why the intermetallic phases with the c-axis doubling distortion are not superconductors and why h-ZrRuP has a higher T(c) than does o-ZrRuP.}, number={26}, journal={INORGANIC CHEMISTRY}, author={Seo, DK and Ren, JQ and Whangbo, MH and Canadell, E}, year={1997}, month={Dec}, pages={6058–6063} }
 @article{greenblatt_zhang_whangbo_1997, title={Electronic properties of La3Ni2O7 and Ln(4)Ni(3)O(10), Ln=La, Pr and Nd}, volume={85}, ISSN={["0379-6779"]}, DOI={10.1016/S0379-6779(97)80312-8}, abstractNote={Abstract Single-phase samples of La3Ni2O7-δ with δ=0, 0.08, 0.16 and 0.65, and Ln4Ni3O10. Ln=La, Pr and Nd were prepared and studied by powder X-ray diffraction, thermogravimetric analysis, electrical resistivity and magnetic susceptibility. The as prepared sample, La3Ni2O6.92 and the fully reduced La3Ni2O6.35 are semiconducting, while the oxygenated La3Ni2O7.0 is metallic For Ln4Ni3O10-δ, when Ln = La, 8 is zero and the material is metallic and Pauli paramagnetic; when Ln = Pr and Nd, δ is ~ 0.15 and an anomaly indicating a metal-to-metal transition is observed at 145 K for Pr4Ni3O10-δ, and 165 K for Nd4Ni3O10-δ. The electrical properties of the homologous series Lan+1NinO3n+1 with n=2,3 are discussed and compared in terms of the dimensionality of the crystal lattice and the electronic band structure calculated by the extended Huckel tight binding method.}, number={1-3}, journal={SYNTHETIC METALS}, author={Greenblatt, M and Zhang, Z and Whangbo, MH}, year={1997}, month={Feb}, pages={1451–1452} }
 @article{bar_thomann_brandsch_cantow_whangbo_1997, title={Factors affecting the height and phase images in tapping mode atomic force microscopy. Study of phase-separated polymer blends of poly(ethene-co-styrene) and poly(2,6-dimethyl-1,4-phenylene oxide)}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la970091m}, abstractNote={Blends of two polymers, poly(ethene-co-styrene) (PES) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), were examined with tapping mode atomic force microscopy (AFM) using various values of the driving amplitude A0 and set-point amplitude ratio rsp = Asp/A0, where Asp is the set-point amplitude. In height and phase images of PPO/PES blend samples, the relative contrast of chemically different regions depends sensitively on the rsp and A0 values. As the tip−sample force is increased from small to large, both phase and height images of PPO/PES blend samples can undergo a contrast reversal twice. This makes it difficult to assign the features of height and phase images to different chemical components without performing additional experiments. Phase and height images were interpreted by analyzing several factors that affect the dependence of phase shift and amplitude damping on rsp and A0.}, number={14}, journal={LANGMUIR}, author={Bar, G and Thomann, Y and Brandsch, R and Cantow, HJ and Whangbo, MH}, year={1997}, month={Jul}, pages={3807–3812} }
 @article{shreevekeyer_haushalter_lee_li_oconnor_seo_whangbo_1997, title={New layered materials in the K-In-Ge-As system: K8In8Ge5As17 and K5In5Ge5As14}, volume={130}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1996.7210}, abstractNote={Exploratory synthesis in the K–In–Ge–As system has yielded the unusual layered compounds K8In8Ge5As17(1) and K5In5Ge5As14(2), both of which contain In–Ge–As layers with interleaved potassium ions, Ge–Ge bonds, InAs4tetrahedra, As–As bonds, and rows of Ge2As6dimers. Compound 1 has As3groups, while compound 2 has infinite As ribbons on both faces of each layer. Unlike compound 1, compound 2 has substitutional defects where indium partially occupies each of the three independent germanium sites in the ratio of 1:5 for In:Ge. This partial occupancy makes 2 an electron-precise compound. The Ge(In)–Ge(In) bond of 2 is longer than the Ge–Ge bond of 1, and this bond lengthening effect was confirmed by performing DFT-MO calculations on the model compounds H3Ge–GeH3and H3Ge–InH−3. Possible implications of electron imprecise formulas determined by X-ray crystal structure determinations are discussed. Compound 1: space groupP21/cwitha=18.394 (8) Å,b=19.087 (7) Å,c=25.360 (3) Å,β=105.71 (2)°,V=8571 (4) Å3, andDcalcd=4.45g/cm3forZ=4. Refinement on 4455 reflections yieldedR(Rw)=6.8%(7.8%). Compound 2: space groupC2/mwitha=40.00 (1) Å,b=3.925 (2) Å,c=10.299 (3),β=99.97 (2)°,V=1592 (1) Å3, andDcalcd= 4.55g/cm3forZ=8. Refinement on 1206 reflections yieldedR(Rw)=5.6% (5.7%).}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={ShreeveKeyer, JL and Haushalter, RC and Lee, YS and Li, SC and OConnor, CJ and Seo, DK and Whangbo, MH}, year={1997}, month={May}, pages={234–249} }
 @misc{brandsch_bar_whangbo_1997, title={On the factors affecting the contrast of height and phase images in tapping mode atomic force microscopy}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la970822i}, abstractNote={Tapping mode atomic force microscopy measurements were performed for patterned self-assembled monolayers (SAMs) of −S(CH2)15CH3 and −S(CH2)15COOH groups on a polycrystalline Au substrate. Height and phase images of these SAMs were obtained as a function of the driving amplitude A0 and the set-point amplitude Asp. Factors influencing the contrasts of these images are discussed in terms of the simple approximation that the essential consequence of bringing the tip closer to the sample surface is to change the force constant of the cantilever.}, number={24}, journal={LANGMUIR}, author={Brandsch, R and Bar, G and Whangbo, MH}, year={1997}, month={Nov}, pages={6349–6353} }
 @article{dhingra_seo_kowach_kremer_shreevekeyer_haushalter_whangbo_1997, title={One-dimensional semiconducting chains of the quaternary zintl anion in (Et4N)(4)[Au(Ag1-xAux)(2)Sn2Te9]}, volume={36}, ISSN={["0570-0833"]}, DOI={10.1002/anie.199710871}, abstractNote={Metal atoms in isolated chains are the sole components of the first quaternary Zintl anion [Au(Ag1-xAux)2Sn2Te9]-4 (x = 0.32; structure of depicted below) in the compound (Et4N4)[Au(Ag1-xAux)2Sn2Te9]. Electronic structure calculations and the diamagnetic and semiconducting properties of of this new compound show that the anion displays a Peierls distortion at room temperature.}, number={10}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH}, author={Dhingra, SS and Seo, DK and Kowach, GR and Kremer, RK and ShreeveKeyer, JL and Haushalter, RC and Whangbo, MH}, year={1997}, month={Jun}, pages={1087–1090} }
 @article{gupta_seo_whangbo_jobic_rouxel_brec_1997, title={Square planar to rectangular distortion in transition-metal compounds of edge-sharing square planar units MX(4)}, volume={128}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1996.7177}, abstractNote={In transition metal compounds of edge-sharing square planarMX4units (M=group 10, group 11;X=O, S, Se), a square planar to rectangular distortion is observed. The causes for this distortion inMX2ladder chains,M3X4honeycomb layers, and 3DMXlattices were examined by performing extended Hückel tight binding electronic band structure calculations. The primary cause for the distortion is the reduction of the four-electron two-orbital destabilizing interactions among thep-orbitals ofX.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Gupta, N and Seo, DK and Whangbo, MH and Jobic, S and Rouxel, J and Brec, R}, year={1997}, month={Feb}, pages={181–184} }
 @misc{lee_seo_whangbo_1997, title={Structural and electronic factors governing the metallic and nonmetallic properties of the pyrochlores A(2)Ru(2)O(7-y)}, volume={131}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1997.7497}, abstractNote={The metal-versus-semiconductor behavior of ruthenium pyrochloresA2Ru2O7−ywas examined by calculating their electronic band structures. This behavior is explained in terms of the Mott–Hubbard mechanism of electron localization. The width of thet2g-block bands ofA2Ru2O7−yincreases with increasing Ru–O–Ru bond angle, and the Ru–O–Ru angle increases with increasing size of theAcation. There is a good linear relationship between the ionic radius of theAcation and the Ru–O–Ru bond angle. This relationship makes it possible to calculate the amount of the O′ atom vacancy based on the observed Ru–O–Ru angle in Tl2Ru2O7−y.}, number={2}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Lee, KS and Seo, DK and Whangbo, MH}, year={1997}, month={Jul}, pages={405–408} }
 @article{hillebrecht_schmidt_rotter_thiele_zonnchen_bengel_cantow_magonov_whangbo_1997, title={Structural and scanning microscopy studies of layered compounds MCl(3) (M=Mo, Ru, Cr) and MOCl(2) (M=V, Nb, Mo, Ru, Os)}, volume={246}, ISSN={["0925-8388"]}, DOI={10.1016/S0925-8388(96)02465-6}, abstractNote={Structural investigations on trichlorides (α- and β-MoCl3, solid solutions Ru1−5CrxCl3) and oxide dichlorides MOCl2 (M = V, Nb, Mo, Ru, Os) show that layer structures with stacking faults can be solved without evaluation of the diffuse parts of scattering. The combination of X-ray methods and atomic scale STM/AFM imaging yields information about the pattern of the surface atoms and the metal sublattice between the halide layers. Metal-metal bonds, structural distortions of coordination polyhedra and cation distribution in solid solutions have been determined. The correct layer symmetry, obtained by STM/AFM methods, was used in the X-ray structure analysis by single crystal and powder diffraction. Disorder problems due to stacking faults of the layers could be treated in that way.}, number={1-2}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Hillebrecht, H and Schmidt, PJ and Rotter, HW and Thiele, G and Zonnchen, P and Bengel, H and Cantow, HJ and Magonov, SN and Whangbo, MH}, year={1997}, month={Jan}, pages={70–79} }
 @article{seo_perdue_ren_whangbo_1997, title={Study of scanning tunneling microscopy images and probable relaxations of the SrTiO3(100) surface by electronic structure calculations}, volume={370}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(97)80003-9}, abstractNote={Abstract Partial electron density plots were calculated for a model SrTiO 3 (100) surface with √5 × √5 ordered oxygen vacancy to examine why the bright spots of the scanning tunneling microscopy (STM) images of SrTiO 3 (100) observed in ultrahigh vacuum (UHV) correspond to the oxygen vacancy sites. Possible dependence of the image on the polarity and magnitude of the bias voltage was also discussed on the basis of partial electron density plot calculations. Our study strongly suggests that the UHV STM imaging involves the lowest-lying d-block level of every two Ti 3+ centers adjacent to an oxygen vacancy, the tip-sample distance involved in the UHV STM experiments is substantially larger than that involved in typical ambient-condition STM imaging, and the Ti 4+ and Ti 3+ sites of SrTiO 3 (100) are reconstructed.}, number={2-3}, journal={SURFACE SCIENCE}, author={Seo, DK and Perdue, K and Ren, J and Whangbo, MH}, year={1997}, month={Jan}, pages={245–251} }
 @article{seo_ren_whangbo_1997, title={Study of the origin of superstructure patterns in the scanning tunneling images of perylene-3,4,9,10-tetracarboxylic-dianhydride on graphite by electronic structure calculations}, volume={370}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(96)00948-X}, abstractNote={Partial electron density plots were calculated for various arrangements of perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) molecules on graphite to understand why scanning tunneling microscopy (STM) images of PTCDA on graphite exhibit superstructure contrast variations. In agreement with experiment, the contrast of the partial electron density plot depends strongly on the orientation and position of PTCDA on graphite. This observation originates from the fact that the overlap between the orbitals of the adsorbate and substrate is strongly affected by their relative arrangement. The HOMO or LUMO density of an adsorbate molecule can be inadequate in interpreting STM images of adsorbate molecules.}, number={2-3}, journal={SURFACE SCIENCE}, author={Seo, DK and Ren, J and Whangbo, MH}, year={1997}, month={Jan}, pages={252–258} }
 @article{seo_whangbo_1997, title={Symmetric stretching vibrations of two-coordinate oxygen bridges as a cause for negative thermal expansion in zrv(x)p(2)-(x)o(7) and aw(2)o(8) (a=zr, hf) at high temperature}, volume={129}, DOI={10.1006/jssc.1997.7301}, abstractNote={To examine the origin of negative thermal expansion in oxides ZrVxP2−xO7(x=0–2) andAW2O8(A=Zr, Hf),ab initioself-consistent-field molecular orbital calculations were carried out for a model compound (HO)3P–O–P(OH)2+3. Our study suggests that symmetric stretching vibrations of two-coordinate oxygen bridges are strongly coupled with their bending vibrations and are more important for negative thermal expansion at high temperature. The oxygen bridges accomodate a large stretching of theA–O (A=Zr, Hf) andM–O (M=P,V) bonds at high temperature by decreasing the bond angles of the oxygen bridges. When the bond angles increase, the bonds are shortened due to the π-type orbital interactions associated with the oxygen lone pair orbitals.}, number={1}, journal={Journal of Solid State Chemistry}, author={Seo, D. K. and Whangbo, M.-H.}, year={1997}, pages={160–163} }
 @article{magonov_cleveland_elings_denley_whangbo_1997, title={Tapping-mode atomic force microscopy study of the near-surface composition of a styrene-butadiene-styrene triblock copolymer film}, volume={389}, ISSN={["0039-6028"]}, DOI={10.1016/S0039-6028(97)00412-3}, abstractNote={Thin films of a styrene-butadiene-styrene triblock copolymer were examined by tapping-mode atomic force microscopy at different levels of tip-sample forces. The height images recorded at minimal forces show the surface topography of the topmost butadiene-rich layer. As the level of the tip-sample force is increased, the height and phase images gradually undergo local changes and eventually reveal patterns of a microphase separation which forms underneath the topmost butadiene-rich layer. The contrast variations of the phase and height images are caused by differences in the interaction of the tip with styrene and butadiene blocks, and their qualitative trends are explained by taking into account the change of the effective resonance frequency of the interacting cantilever. The relative contrast of styrene and butadiene blocks depends sensitively on the driving frequency in height images, but not in phase images.}, number={1-3}, journal={SURFACE SCIENCE}, author={Magonov, SN and Cleveland, J and Elings, V and Denley, D and Whangbo, MH}, year={1997}, month={Nov}, pages={201–211} }
 @article{lee_seo_whangbo_li_mackay_hwu_1997, title={Vacancy ordering as the cause for the electrical resistivity anomalies and superlattice modulations in ACu(7-x)S(4) (A = Tl, K, Rb)}, volume={134}, ISSN={["0022-4596"]}, DOI={10.1006/jssc.1997.7506}, abstractNote={The electronic structure of KCu7S4was calculated using the extended Hückel tight binding method, and the origin of the resistivity anomalies and the superlattice reflections ofACu7−xS4(A=Tl, K, Rb) was probed. The present work shows thatACu7−xS4(A=Tl, K, Rb) can be metallic only forx>0 and that the superlattice modulations ofACu7−xS4(A=Tl, K, Rb) are caused by the vacancy ordering in the Cu(2) atom sites. The resistivity anomalies ofACu7−xS4are explained in terms of the vacancy ordering in the Cu(2)–Cu(2) chains.}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Lee, KS and Seo, DK and Whangbo, MH and Li, H and Mackay, R and Hwu, SJ}, year={1997}, month={Nov}, pages={5–9} }
 @misc{canadell_whangbo_1991, title={CONCEPTUAL ASPECTS OF STRUCTURE PROPERTY CORRELATIONS AND ELECTRONIC INSTABILITIES, WITH APPLICATIONS TO LOW-DIMENSIONAL TRANSITION-METAL OXIDES}, volume={91}, ISSN={["0009-2665"]}, DOI={10.1021/cr00005a015}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConceptual aspects of structure-property correlations and electronic instabilities, with applications to low-dimensional transition-metal oxidesEnric. Canadell and Myung Hwan. WhangboCite this: Chem. Rev. 1991, 91, 5, 965–1034Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July 1991https://doi.org/10.1021/cr00005a015RIGHTS & PERMISSIONSArticle Views1576Altmetric-Citations263LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (7 MB) Get e-Alerts Get e-Alerts}, number={5}, journal={CHEMICAL REVIEWS}, author={CANADELL, E and WHANGBO, MH}, year={1991}, pages={965–1034} }
 @misc{williams_schultz_geiser_carlson_kini_wang_kwok_whangbo_schirber_1991, title={ORGANIC SUPERCONDUCTORS - NEW BENCHMARKS}, volume={252}, ISSN={["1095-9203"]}, DOI={10.1126/science.252.5012.1501}, abstractNote={Recent advances in the design and synthesis of organic synthetic metals have yielded materials that have the highest superconducting transition temperatures (T(c) approximately 13 kelvin) reported for these systems. These materials have crystal structures consisting of alternating layers of organic donor molecules and inorganic anions. Organic superconductors have various electronic and magnetic properties and crystal structures that are similar to those of the inorganic copper oxide superconductors (which have high T(c) values); these similarities include highly anisotropic conductivities, critical fields, and short coherence lengths. The largest number of organic superconductors, including those with the highest T(c) values, are charge-transfer salts derived from the electron donor molecule BEDT-TTF or ET [bis(ethylenedithio)-tetrathiafulvalene]. The synthesis and crystal structures of these salts are discussed; their electrical, magnetic, and band electronic structure properties and their many similarities to the copper oxide superconductors are treated as well.}, number={5012}, journal={SCIENCE}, author={WILLIAMS, JM and SCHULTZ, AJ and GEISER, U and CARLSON, KD and KINI, AM and WANG, HH and KWOK, WK and WHANGBO, MH and SCHIRBER, JE}, year={1991}, month={Jun}, pages={1501–1508} }
 @article{kini_geiser_wang_carlson_williams_kwok_vandervoort_thompson_stupka_jung_et al._1990, title={A NEW AMBIENT-PRESSURE ORGANIC SUPERCONDUCTOR, KAPPA-(ET)2CU[N(CN)2]BR, WITH THE HIGHEST TRANSITION-TEMPERATURE YET OBSERVED (INDUCTIVE ONSET TC = 11.6 K, RESISTIVE ONSET = 12.5 K)}, volume={29}, ISSN={["0020-1669"]}, DOI={10.1021/ic00339a004}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA new ambient-pressure organic superconductor, .kappa.-(ET)2Cu[N(CN)2]Br, with the highest transition temperature yet observed (inductive onset Tc = 11.6 K, resistive onset = 12.5 K)Aravinda M. Kini, Urs Geiser, Hau H. Wang, K. Douglas Carlson, Jack M. Williams, W. K. Kwok, K. G. Vandervoort, James E. Thompson, Daniel L. Stupka, and Cite this: Inorg. Chem. 1990, 29, 14, 2555–2557Publication Date (Print):July 1, 1990Publication History Published online1 May 2002Published inissue 1 July 1990https://doi.org/10.1021/ic00339a004Request reuse permissionsArticle Views1581Altmetric-Citations568LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (451 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts}, number={14}, journal={INORGANIC CHEMISTRY}, author={KINI, AM and GEISER, U and WANG, HH and CARLSON, KD and WILLIAMS, JM and KWOK, WK and VANDERVOORT, KG and THOMPSON, JE and STUPKA, DL and JUNG, D and et al.}, year={1990}, month={Jul}, pages={2555–2557} }
 @article{williams_kini_wang_carlson_geiser_montgomery_pyrka_watkins_kommers_boryschuk_et al._1990, title={FROM SEMICONDUCTOR SEMICONDUCTOR TRANSITION (42K) TO THE HIGHEST-12.5 K ORGANIC SUPERCONDUCTOR, KAPPA-(ET)2CU[N(CN)2]CL}, volume={29}, ISSN={["0020-1669"]}, DOI={10.1021/ic00343a003}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFrom semiconductor-semiconductor transition (42 K) to the highest-Tc organic superconductor, .kappa.-(ET)2Cu[N(CN)2]Cl (Tc = 12.5 K)Jack M. Williams, Aravinda M. Kini, Hau H. Wang, K. Douglas Carlson, Urs Geiser, Lawrence K. Montgomery, Gloria J. Pyrka, Diana M. Watkins, Jefferson M. Kommers, and Cite this: Inorg. Chem. 1990, 29, 18, 3272–3274Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990https://doi.org/10.1021/ic00343a003RIGHTS & PERMISSIONSArticle Views1023Altmetric-Citations426LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (384 KB) Get e-Alerts Get e-Alerts}, number={18}, journal={INORGANIC CHEMISTRY}, author={WILLIAMS, JM and KINI, AM and WANG, HH and CARLSON, KD and GEISER, U and MONTGOMERY, LK and PYRKA, GJ and WATKINS, DM and KOMMERS, JM and BORYSCHUK, SJ and et al.}, year={1990}, month={Sep}, pages={3272–3274} }
 @misc{williams_wang_emge_geiser_beno_leung_carlson_thorn_schultz_whangbo_1987, title={RATIONAL DESIGN OF SYNTHETIC METAL SUPERCONDUCTORS}, volume={35}, ISSN={["0079-6379"]}, DOI={10.1002/9780470166369.ch2}, journal={PROGRESS IN INORGANIC CHEMISTRY}, author={WILLIAMS, JM and WANG, HH and EMGE, TJ and GEISER, U and BENO, MA and LEUNG, PCW and CARLSON, KD and THORN, RJ and SCHULTZ, AJ and WHANGBO, MH}, year={1987}, pages={51–218} }