@article{kim_wang_lu_nardelli_bernholc_2008, title={Effects of end group functionalization and level alignment on electron transport in molecular devices}, volume={128}, number={2}, journal={Journal of Chemical Physics}, author={Kim, G. and Wang, S. C. and Lu, W. C. and Nardelli, M. B. and Bernholc, J.}, year={2008} }
 @article{hodak_wang_lu_bernholc_2007, title={Implementation of ultrasoft pseudopotentials in large-scale grid-based electronic structure calculations}, volume={76}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.76.085108}, abstractNote={An implementation of Vanderbilt ultrasoft pseudopotentials in real-space grid-based electronic structure calculations is presented. Efficient utilization of these pseudopotentials requires the use of different grids for i wave functions, ii charge density, and iii sharply peaked operators within the atomic core radii. High-order interpolation between the various grids is important for accuracy, as is high-order discretization for the differential operators. However, efficiency is also of paramount importance, especially when parallelizing over hundreds or thousands of processors. We describe algorithms and procedures used to achieve an effective implementation in the real-space multigrid code, and provide test results for first-row diatomics, bulk transition metals, and energy-conserving quantum molecular dynamics of water. The code parallelizes efficiently over several thousands of processors on modern parallel supercomputers, such as the Cray XT3 and XT4.}, number={8}, journal={PHYSICAL REVIEW B}, author={Hodak, Miroslav and Wang, Shuchun and Lu, Wenchang and Bernholc, J.}, year={2007}, month={Aug} }
 @article{wang_lu_zhao_bernholc_2006, title={Resonant coupling and negative differential resistance in metal/ferrocenyl alkanethiolate/STM structures}, volume={74}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.74.195430}, abstractNote={Recent experimental studies demonstrated that self-assembled molecules sandwiched between metallic contacts can perform logic functions based on negative differential resistance NDR. To understand the mechanism of NDR, the electronic structure and transport properties of one such junction, ferrocenyl alkanethiolate attached to a gold surface and probed with a scanning tunneling microscope tip, are investigated by large scale ab initio calculations. The I-V characteristics show strong NDR features at both positive and negative biases, in good agreement with the experimental data. The voltage-dependent transmission, potential drop profile, and molecular level alignment under bias suggest that the ferrocenyl group acts like a quantum dot and that the NDR features are due to resonant coupling between the highest occupied molecular orbital and the density of states of gold leads. The strength of the individual NDR peaks can be tuned by changing the tunneling distance or using suitable spacer layers.}, number={19}, journal={PHYSICAL REVIEW B}, author={Wang, Shuchun and Lu, Wenchang and Zhao, Qingzhong and Bernholc, J.}, year={2006}, month={Nov} }
 @article{schmidt_seino_hahn_bechstedt_lu_wang_bernholc_2004, title={Calculation of surface optical properties: from qualitative understanding to quantitative predictions}, volume={455}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2003.11.263}, abstractNote={In the last couple of years there has been much methodological and computational progress in the modeling of optical properties from first principles. While the calculation of non-linear optical coefficients is still hampered by numerical limitations—demonstrated here for the case of bulk GaAs—linear optical spectra can now be calculated accurately and with true predictive power, even for large and complex surface structures. This allows on one hand for a much better understanding of the origin of specific features such as surface optical anisotropies. We find that in particular microscopic electric fields at the surface induce slight deformations of bulk-like wavefunctions and thus give rise to optical anisotropies even from sub-surface layers. On the other hand, from the comparison of measured and calculated spectra, one can now confidently reach conclusions on the surface geometry. This short review focuses on the simulation of reflectance anisotropy spectroscopy. The clean, hydrogenated and uracil-covered Si(001) surface is used to illustrate the microscopic origin of surface optical anisotropies and the present state-of-the-art in computational modeling of optical spectra.}, number={2004 May 1}, journal={THIN SOLID FILMS}, author={Schmidt, WG and Seino, K and Hahn, PH and Bechstedt, E and Lu, W and Wang, S and Bernholc, J}, year={2004}, month={May}, pages={764-+} }
 @article{fleischer_chandola_esser_richter_mcgilp_schmidt_wang_lu_bernholc_2004, title={Determination of the electron inelastic mean free path in some binary alloys for application in quantitative surface analysis}, volume={235}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2004.05.117}, abstractNote={Quantitative surface- and thin film analysis by electron spectroscopies (AES, XPS, EELS) requires the knowledge of one of the most important parameters of the electron transport such as the inelastic mean free path (IMFP) of electrons. Numerous data on the IMFP have been already published, mainly for elemental solids and some inorganic and organic compounds. However, the IMFPs for some binary alloy systems are still lacking. Although IMFP values for complex solids can be calculated from predictive formulae, IMFPs can be also measured experimentally by elastic peak electron spectroscopy (EPES). The present work is dealing with the experimental determination of the IMFP in selected binary alloys, i.e. AuxCu100−x (x=25, 75 at.%), AuxPd100−x (x=10, 90 at.%) and AuxNi100−x (x=5 at.%) within the 200–2000 eV range. The relative EPES experiments have been performed using a double-pass CMA spectrometer and the Ni standard. The measured IMFPs were compared with IMFPs calculated from the TPP-2M predictive formula. The RMS deviation from IMFP values calculated from the TPP-2M equation was 0.6–2.5 Å depending on the alloy surface composition, and it was smallest for the Au5Ni95 alloy. The mean percentage deviation from the TPP-2M IMFPs was 4.3–17.6%.}, number={1-2}, journal={APPLIED SURFACE SCIENCE}, author={Fleischer, K. and Chandola, S. and Esser, N. and Richter, W. and McGilp, J. F. and Schmidt, W. G. and Wang, S. and Lu, W. and Bernholc, Jerzy}, year={2004}, month={Jul}, pages={15–20} }
 @article{schmidt_fuchs_hermann_seino_bechstedt_passmann_wahl_gensch_hinrichs_esser_et al._2004, title={Oxidation- and organic-molecule-induced changes of the Si surface optical anisotropy: ab initio predictions}, volume={16}, ISSN={["1361-648X"]}, DOI={10.1088/0953-8984/16/39/007}, abstractNote={In the last couple of years there has been much methodological and computational progress in the modelling of optical properties from first principles. Reflectance anisotropy spectra (RAS) can now be calculated with true predictive power and can thus be used to draw conclusions directly on the surface geometry. In the present work we study two potentially very interesting applications for RAS: the oxidation of Si(001) and the functionalization of the Si surface with organic molecules. Our calculations confirm experimental indications that the polarity of the interface-induced optical anisotropy is reversed layer by layer with increasing oxide thickness. The oscillation of the RAS amplitude should thus allow for the quantitative monitoring of the vertical progression of the oxidation. Our results for Si(001) surfaces modified by cyclopentene and 9,10-phenanthrenequinone adsorption show a strong sensitivity of the RAS signal with respect to the adsorption geometry. Comparison with experimental data shows that cyclopentene most probably adsorbs via a cycloaddition reaction with the Si surface dimers, while phenanthrenequinone seems to adsorb across two Si dimers.}, number={39}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Schmidt, WG and Fuchs, F and Hermann, A and Seino, K and Bechstedt, F and Passmann, R and Wahl, M and Gensch, M and Hinrichs, K and Esser, N and et al.}, year={2004}, month={Oct}, pages={S4323–S4334} }
 @article{wang_lu_schmidt_bernholc_2003, title={Nanowire-induced optical anisotropy of the Si(111)-In surface}, volume={68}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.68.035329}, abstractNote={Ab initio calculations of the reflectance anisotropy of Si(111)-In surfaces are presented. A very pronounced optical anisotropy around 2 eV is predicted for the structural model proposed by Bunk et al. [Phys. Rev. B 59, 12 228 (1999)] for the (4 × 1) reconstructed surface. The (4 X 2)/(8 × 2) reconstructed surface, induced by a slight distortion of the indium chains, is shown to result in a splitting of the 2 eV peak. The calculated results are in excellent agreement with recent polarized reflectance data acquired during the (4×1)→(4×2)/ (8×2) phase transition.}, number={3}, journal={PHYSICAL REVIEW B}, author={Wang, SC and Lu, WC and Schmidt, WG and Bernholc, J}, year={2003}, month={Jul} }