@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={Abstract Electronic structures of phosphosilicides Cu4SiP8, IrSi3P3, CoSi3P3, and FeSi4P4 were calculated using the extended Huckel 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{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} }
 @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{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{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} }
 @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_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{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} }