@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={Abstract}, 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{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{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 mu-HCO2- and mu-pyz ligands to form a highly corrugated two-dimensional layered network. Bulk magnetic measurements show a broad maximum in chi(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 = -JSigmaSi x 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 chi'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{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{lu_dai_yang_li_2006, title={Atomic orbitals in molecules: general electronegativity and improvement of Mulliken population analysis}, volume={8}, ISSN={["1463-9084"]}, DOI={10.1039/b511516g}, abstractNote={An approach of atomic orbitals in molecules (AOIM) has been developed to study the atomic properties in molecules, in which the molecular orbitals are expressed in terms of the optimized minimal atomic orbitals. The atomic electronegativities are calculated using Pauling's electronegativity of free atom and are employed to find the electronegativity equilibrium in molecules and to describe the amphoteric properties of the transition metals from the groups 4 to 10. AOIM can also improve the numerical stability and accuracy of the original Mulliken population analysis.}, number={3}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Lu, HG and Dai, D and Yang, P and Li, LM}, year={2006}, month={Jan}, pages={340–346} }
 @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., alpha-AgCuPO4) was determined by powder X-ray diffraction and was compared with that of the high-temperature form of AgCuPO4 (i.e., beta-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; beta-AgCuPO4 has two Cu2P2O8 layers per unit cell, while alpha-AgCuPO4 has one. The coordinate environment of each Cu2+ ion is close to being a distorted square pyramid in alpha-AgCuPO4, but it is close to being a distorted trigonal bipyramid in beta-AgCuPO4. The magnetic susceptibilities of alpha- and beta-AgCuPO4 are well simulated by an antiferromagnetic alternating-chain model, which leads to J/k(B) = -146.1 K and alphaJ/k(B) = -75.8 K for alpha-AgCuPO4, and J/k(B) = -82.6 K and alphaJ/k(B) = -31.7 K for beta-AgCuPO4 (with the convention in which the spin-exchange parameter between two adjacent spin sites is written as 2J). The spin gaps, delta/k(B), obtained from these parameters are 93.7 K for alpha-AgCuPO4 and 62.3 K for beta-AgCuPO4. The strongest spin exchange in both forms of AgCuPO4 comes from a super-superexchange path, and this interaction is stronger for alpha-AgCuPO4 than for beta-AgCuPO4 by a factor of approximately 2, in good agreement with the experiment. Our analysis supports the use of this model for beta-AgCuPO4 and indicates that the spin lattice of alpha-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{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 NaxCoO2 (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 NaxCoO2 (x ≈ 0.75), and implications of this analysis were explored. Our study shows that the low-spin Co4+ (S = 1/2) ions of NaxCoO2 generated by the Na vacancies cause the anisotropic magnetic properties of NaxCoO2 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 NaxCoO2 is more negative along the direction of the lower g factor (i.e., θ∥ < θ⊥ < 0 and g∥ < g⊥). The occurrence of intermediate-spin Co3+ ions surrounding each Co4+ ion accounts for the apparently puzzling magnetic properties of NaxCoO2 (x ≈ 0.75), i.e., the large negat...}, number={15}, journal={INORGANIC CHEMISTRY}, author={Whangbo, M. -H. and Dai, D. and Kremer, R. K.}, year={2006}, month={Jul}, pages={5989–5995} }
 @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{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 d(6) 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 Ca(3)Co(2)O(6) with high-spin Co(3+) (d(6)) ions at the trigonal prism sites and those of Fe[C(SiMe(3))(3)](2) with high-spin Fe(2+) (d(6)) ions at linear two-coordinate sites, and discussed why compounds with high-spin d(6) 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{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-mu-(N3)2(N3)2], 1; [Cu2(terpy)2-mu-(N3)4Cu2-mu-(N3)2(N3)2], 2; and[Cu2(terpy)2-mu-(N3)2(N3)2Cu3-mu-(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{huang_dai_long_yan_dai_2005, title={Fermi-energy and minimum diameter for metallic silver cluster}, volume={19}, number={15-17}, journal={International Journal of Modern Physics. B, Condensed Matter Physics, Statistical Physics, Applied Physics}, author={Huang, B. B. and Dai, Y. and Long, R. and Yan, C. X. and Dai, D.}, year={2005}, pages={2404–2408} }
 @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 Cu(2+) ion arrangements in the magnetic oxides A(2)Cu(PO(4))(2) (A = Ba, Sr), ACuP(2)O(7) (Ba, Ca, Sr, Pb), CaCuGe(2)O(6), and Cu(2)UO(2)(PO(4))(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{dai_dai_yan_huang_han_2005, title={N-type electric conductivity of nitrogen-doped ultrananocrystalline diamond films}, volume={71}, number={7}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Dai, Y. and Dai, D. and Yan, C. X. and Huang, B. B. and Han, S. H.}, year={2005} }
 @article{dai_dai_huang_yan_2005, title={Size-dependent metal-nonmetal change of groups IB and IIB metal clusters}, volume={34}, number={03-Jan}, journal={European Physical Journal. D, Atomic, Molecular and Optical Physics}, author={Dai, Y. and Dai, D. and Huang, B. and Yan, C.}, year={2005}, pages={105–107} }
 @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{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{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{dai_dai_liu_han_huang_2004, title={Mechanism of p-type-to-n-type conductivity conversion in boron-doped diamond}, volume={84}, ISSN={["0003-6951"]}, DOI={10.1063/1.1650909}, abstractNote={We report on the role of two boron–hydrogen complexes in the conductivity conversion from p-type to n-type in boron-doped diamond samples. The calculated electronic structures of the simulated clusters show that the boron–hydrogen complex of hydrogen–boron pairs (BH1) is characteristic of p-type conductivity, and that of two hydrogen–boron centers (BH2) or three-hydrogen-boron centers (BH3) have a character of n-type conductivity. The phenomenon of conversion from p-type-to-n-type conductivity through deuteration may be explained by the transformation from the BH1 into BH2 and/or BH3 complexes.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Dai, Y and Dai, D and Liu, DH and Han, SH and Huang, BB}, year={2004}, month={Mar}, pages={1895–1897} }
 @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{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={First principles spin-polarized electronic band structure calculations were carried out for three ordered spin states of CdVO3, and the strengths of its corner- and edge-sharing spin exchange interactions were estimated. To gain insight into why CdVO3 exhibits ferromagnetism while CaV2O5 does not despite their apparent structural similarity, the spin exchange interactions of CdVO3 and CaV2O5 were compared in terms of spin dimer analysis using extended Hückel tight binding calculations, and the local geometries of their V4+ 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{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{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{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{dai_han_huang_dai_2003, title={Study on n-type doping with phosphorous in diamond by means of density functional theory}, volume={99}, number={03-Jan}, journal={Materials Science & Engineering. B, Solid-state Materials for Advanced Technology}, author={Dai, Y. and Han, S. G. and Huang, B. B. and Dai, D. D.}, year={2003}, pages={531–535} }
 @article{dai_han_dai_zhang_qi_2003, title={Surface passivant effects on electronic states of the band edge in Si-nanocrystals}, volume={126}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(03)00086-3}, abstractNote={We studied the effect of the surface passivants fluorine (F), chlorine (Cl), oxygen (O) and oxygen-related OH on the energy band edge states of clusters with the same Si29 and Si47 core by means of the atomic cluster model and density functional theory (DFT). The results confirm that the electronic states of the band edge in clusters are sensitive to these passivants, and the passivant O that may form double bonded structure affects the band edge states most strongly. The results may be helpful for understanding and controlling the electrical and optical properties of nanocrystalline silicon.}, number={3}, journal={SOLID STATE COMMUNICATIONS}, author={Dai, Y and Han, SH and Dai, DD and Zhang, Y and Qi, Y}, year={2003}, month={Apr}, pages={103–106} }
 @article{dai_huang_dai_2003, title={The role of dangling-bond, hydrogen and adsorbate in diamond surface conduction}, volume={12}, ISSN={["1879-0062"]}, DOI={10.1016/S0925-9635(02)00244-3}, abstractNote={The mechanism of surface conductivity (SC) in diamond, concerning the role of dangling-bond, hydrogen and adsorbate, has been investigated by density functional theory calculations of simulating clusters. We have deduced two possible mechanisms for the SC: one originates from the transport of electron in the localized states near the Fermi level, and another one from the holes in the extended states at about the mobility edge. These models may help one understand most of the experimental results qualitatively or quantitatively in order.}, number={1}, journal={DIAMOND AND RELATED MATERIALS}, author={Dai, Y and Huang, BB and Dai, DD}, year={2003}, month={Jan}, pages={15–19} }
 @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{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={Abstract 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{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{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{dai_dai_ding_2001, title={Study on multiphoton processes in intense laser fields using the quadratic anharmonic Lie algebraic hamiltonian of diatomic molecule}, volume={271}, ISSN={["0301-0104"]}, DOI={10.1016/S0301-0104(01)00444-X}, abstractNote={Abstract The quadratic anharmonic Lie algebraic hamiltonian of a non-rotation Mores oscillator is used to study the multiphoton processes of diatomic molecule placed in intense laser fields. The averaged absorb energy spectra of multiphoton transition are calculated. The long-time behaviors and the effect of laser phase in multiphoton process also are investigated.}, number={1-2}, journal={CHEMICAL PHYSICS}, author={Dai, Y and Dai, DD and Ding, SL}, year={2001}, month={Sep}, pages={71–78} }