@article{bernholc_lu_nakhmanson_hahn_meunier_nardelli_schmidt_2007, title={Atomic scale design of nanostructures}, volume={105}, ISSN={["1362-3028"]}, DOI={10.1080/00268970701189186}, abstractNote={Recent advances in theoretical methods and high performance computing allow for reliable first-principles predictions of complex nanostructured materials and devices. This paper describes three examples: (i) non-equilibrium electron transport through molecular junctions, as a stepping stone for the design of molecular-scale devices and for integration of biomolecules with Si technology; (ii) polarization and piezoelectric properties of PVDF and related polymers; and (iii) the many-body optical spectrum of water. For the molecular junction, our results provide a qualitative picture and quantitative understanding of the mechanism leading to negative differential resistance for a large class of small molecules. For ferroelectric polymers, the calculations show that their polarization is described by cooperative, quantum-mechanical interactions between polymer chains. Nevertheless, the ab initio results lead to a simple parameterization of polarization as a function of copolymer concentration. Finally, our calculations explain the well-known redshift in the fundamental absorption of water as due to exciton delocalization upon aggregation.}, number={2-3}, journal={MOLECULAR PHYSICS}, author={Bernholc, J. and Lu, W. and Nakhmanson, S. M. and Hahn, P. H. and Meunier, V. and Nardelli, M. Buongiorno and Schmidt, W. G.}, year={2007}, pages={147–156} }
 @article{hahn_schmidt_seino_preuss_bechstedt_bernholc_2005, title={Optical Absorption of Water: Coulomb Effects versus Hydrogen Bonding}, volume={94}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.94.037404}, DOI={10.1103/physrevlett.94.037404}, abstractNote={The optical spectrum of water is not well understood. For example, the main absorption peak shifts upwards by 1.3 eV upon condensation, which is contrary to the behavior expected from aggregation-induced broadening of molecular levels. We investigate theoretically the effects of electron-electron and electron-hole correlations, finding that condensation leads to delocalization of the exciton onto nearby hydrogen-bonded molecules. This reduces its binding energy and has a dramatic impact on the line shape. The calculated spectrum is in excellent agreement with experiment.}, number={3}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Hahn, P. H. and Schmidt, W. G. and Seino, K. and Preuss, M. and Bechstedt, F. and Bernholc, J.}, year={2005}, month={Jan} }
 @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{lu_schmidt_bernholc_2003, title={Cycloaddition reaction versus dimer cleavage at the Si(001): C5H8 interface}, volume={68}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.68.115327}, abstractNote={The interface formed between an ordered monolayer of cyclopentene and silicon is studied by first-principles density-functional calculations. Several different structural models of the interface are considered and their reflectance anisotropy spectra are calculated. The spectra turn out to be highly structure dependent and can therefore be used to monitor the interface formation. We also find that coadsorption of hydrogen, which leads to dimer cleavage, can stabilize the interface by saturating the dangling bonds and releasing the high strain energy.}, number={11}, journal={PHYSICAL REVIEW B}, author={Lu, WC and Schmidt, WG and Bernholc, J}, year={2003}, month={Sep} }
 @article{pristovsek_tsukamoto_ohtake_koguchi_orr_schmidt_bernholc_2003, title={Gallium-rich reconstructions on GaAs(001)}, volume={240}, ISSN={["1521-3951"]}, DOI={10.1002/pssb.200301885}, abstractNote={Abstract}, number={1}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Pristovsek, M and Tsukamoto, S and Ohtake, A and Koguchi, N and Orr, BG and Schmidt, WG and Bernholc, J}, year={2003}, month={Nov}, pages={91–98} }
 @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} }
 @article{schmidt_bechstedt_fleischer_cobet_esser_richter_bernholc_onida_2001, title={GaAs(001): Surface structure and optical properties}, volume={188}, ISSN={["0031-8965"]}, DOI={10.1002/1521-396x(200112)188:4<1401::aid-pssa1401>3.0.co;2-1}, abstractNote={The optical anisotropy of differently reconstructed GaAs(001) surfaces has been analysed both theoretically and experimentally. The atomic structures and RAS spectra are calculated from first principles for the As-rich c(4 × 4) and β2(2 × 4) as well as for the stoichiometric α2(2 × 4) and the Ga-rich ζ(4 × 2) surface phases. These results are compared with spectra recorded at low temperature (40 K). We find good agreement between the calculated and measured data, in particular for the As-rich surface phases. In marked contrast to earlier calculations we find the peak near the E1 critical point energy, characteristic of the β2(2 × 4) surface, to originate from electronic transitions in bulk layers. The experimental data for the Ga-rich (4 × 2) surface phase are less well reproduced, possibly due to surface defects or structural deviations from the ζ(4 × 2) model for the surface geometry.}, number={4}, journal={PHYSICA STATUS SOLIDI A-APPLIED RESEARCH}, author={Schmidt, WG and Bechstedt, F and Fleischer, K and Cobet, C and Esser, N and Richter, W and Bernholc, J and Onida, G}, year={2001}, month={Dec}, pages={1401–1409} }
 @article{schmidt_bechstedt_bernholc_2001, title={Terrace and step contributions to the optical anisotropy of Si(001) surfaces}, volume={63}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.63.045322}, abstractNote={The contributions of atomically flat terraces as well as of SA , SB , andDB steps to the optical anisotropy of Si~001! surfaces have been calculated using a real-space multigrid method together with ab initio pseudopotentials. Our results for ideal (1 32), p(232), andc(234) reconstructed surfaces show a distinct influence of the dimer arrangement on the optical spectra. The calculated spectrum for the Si(001) c(234 surface agrees best with the signal measured for atomically smooth terraces. The significant optical anisotropy around 3 eV observed for vicinal surfaces, however, is induced by surface steps. Both electronic transitions directly at the surface as well as in deeper layers contribute to the optical anisotropy. We identify two mechanisms causing anisotropy signals from layers beneath the surface: the influence of the anisotropic surface potential on the bulk wave functions as well as minor contributions from atomic relaxations caused by surface-induced stress.}, number={4}, journal={PHYSICAL REVIEW B}, author={Schmidt, WG and Bechstedt, F and Bernholc, J}, year={2001}, month={Jan} }
 @article{schmidt_bernholc_bechstedt_2000, title={(001) Surfaces of GaP and InP: structural motifs, electronic states and optical signatures}, volume={166}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(00)00406-2}, abstractNote={We present ab initio calculations on the energetics and geometry, as well as electronic and optical properties of InP and GaP(001) surfaces. Cation-rich conditions lead to the formation of asymmetric cation–anion dimers on top of a (2×4) reconstructed cation-terminated surface. Anion-rich surfaces form c(4×4) reconstructions. Based on the DFT-LDA electronic structure, we compute the reflectance anisotropy of the energetically favoured (2×4) reconstructions. Strong anisotropies in the low-energy region arise from transitions between σ-like cation–cation bonding states and empty dangling bonds. Transitions involving P dimer states and surface modified bulk wave functions contribute at higher energies. The application of GW corrections leads to non-uniform shifts of characteristic peaks and changes the line shape, considerably improving the agreement with experiment.}, number={1-4}, journal={APPLIED SURFACE SCIENCE}, author={Schmidt, WG and Bernholc, J and Bechstedt, F}, year={2000}, month={Oct}, pages={179–184} }
 @article{frisch_vogt_visbeck_hannappel_willig_braun_richter_bernholc_schmidt_esser_et al._2000, title={Angle resolved photoemission spectroscopy of the InP(001) surface}, volume={166}, ISSN={["1873-5584"]}, DOI={10.1016/S0169-4332(00)00431-1}, abstractNote={The P-rich (2×1)/(2×2) and the In-rich (2×4) reconstructions of InP(001) are studied by Angle Resolved Photoemission Spectroscopy (ARPES). Experimental results for the In-rich (2×4) InP(001) surface show two bound surface states and one surface resonance, located at −1.6 eV binding energy. This agrees well with ab-initio calculations. For the P-rich (2×1)/(2×2) InP(001) surface, neither theoretical nor experimental work regarding the electronic surface structure exists until now. We identify two possible surface states showing no discernible dispersion along the Γ&#x0304;–J̄ and Γ&#x0304;–J̄′ directions of the surface Brillouin zone (SBZ). The energetically highest state, located close to the valence band maximum (VBM), is only observed along the [1&#x0304;10] direction and is most likely a P-dimer-bond state. The second state, located at −4.4 eV binding energy, is assigned to a surface resonance.}, number={1-4}, journal={APPLIED SURFACE SCIENCE}, author={Frisch, A. M. and Vogt, P. and Visbeck, S. and Hannappel, T. and Willig, F. and Braun, W. and Richter, W. and Bernholc, Jerzy and Schmidt, W. G. and Esser, N. and et al.}, year={2000}, month={Oct}, pages={224–230} }
 @article{bernholc_briggs_bungaro_nardelli_fattebert_rapcewicz_roland_schmidt_zhao_2000, title={Large-scale applications of real-space multigrid methods to surfaces, nanotubes, and quantum transport}, volume={217}, ISSN={["1521-3951"]}, DOI={10.1002/(sici)1521-3951(200001)217:1<685::aid-pssb685>3.0.co;2-3}, abstractNote={The development and applications of real-space multigrid methods are discussed. Multigrid techniques provide preconditioning and convergence acceleration at all length scales, and therefore lead to particularly efficient algorithms. When using localization regions and optimized, non-orthogonal orbitals, calculations involving over 1000 atoms become practical on massively parallel computers. The applications discussed in this chapter include: (i) dopant incorporation and ordering effects during surface incorporation of boron, which lead to the formation of ordered domains at half-monolayer coverage; (ii) incorporation of Mg into GaN during growth, and in particular the conditions that would lead to maximum p-type doping; (iii) optical fingerprints of surface structures for use in real-time feedback control of growth: and (iv) mechanisms of stress release and quantum transport properties of carbon nanotubes.}, number={1}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Bernholc, J and Briggs, EL and Bungaro, C and Nardelli, MB and Fattebert, JL and Rapcewicz, K and Roland, C and Schmidt, WG and Zhao, Q}, year={2000}, month={Jan}, pages={685–701} }
 @article{lu_schmidt_briggs_bernholc_2000, title={Optical Anisotropy of the SiC(001)-(3×2) Surface: Evidence for the Two-Adlayer Asymmetric-Dimer Model}, volume={85}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/physrevlett.85.4381}, DOI={10.1103/physrevlett.85.4381}, abstractNote={The structure of the ( 3x2) reconstruction of beta-SiC(001) surface has been identified by comparing reflectance anisotropy spectra calculated from first principles with recent measurements. Only the calculations for the two-adlayer asymmetric-dimer model agree with experiment. The two prominent peaks at 3.6 and 5.0 eV found experimentally are assigned to electronic transitions between surface and bulklike electronic states. A further pronounced anisotropy at 2.0 eV, due to transitions between surface states, is predicted.}, number={20}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Lu, Wenchang and Schmidt, W. G. and Briggs, E. L. and Bernholc, J.}, year={2000}, month={Nov}, pages={4381–4384} }
 @article{schmidt_bernholc_2000, title={Step-induced optical anisotropy of Si(111): H surfaces}, volume={61}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.61.7604}, abstractNote={The step-induced optical anisotropy of the hydrogenated Si(111) surface has been calculated using a real-space multigrid method together with ab initio pseudopotentials. The investigated step configurations give rise to relatively similar anisotropy spectra with maxima close to the ${E}_{1}$ and ${E}_{2}$ critical points of the silicon bulk band structure. The spectrum for $〈112\ifmmode\bar\else\textasciimacron\fi{}〉$ steps resembles the reflectance anisotropy for Si(110):H and is in good agreement with measurements for Si(111):H vicinally cut toward $[112\ifmmode\bar\else\textasciimacron\fi{}].$ Our results for $〈1\ifmmode\bar\else\textasciimacron\fi{}1\ifmmode\bar\else\textasciimacron\fi{}2〉$ steps, however, are qualitatively different from the corresponding measurements for surfaces miscut toward $[1\ifmmode\bar\else\textasciimacron\fi{}1\ifmmode\bar\else\textasciimacron\fi{}2].$ This apparent discrepancy can be resolved if the formation of staircaselike structures of monohydride terminated steps is assumed.}, number={11}, journal={PHYSICAL REVIEW B}, author={Schmidt, WG and Bernholc, J}, year={2000}, month={Mar}, pages={7604–7608} }
 @article{schmidt_bechstedt_bernholc_2000, title={Understanding reflectance anisotropy: Surface-state signatures and bulk-related features}, volume={18}, ISSN={["1071-1023"]}, DOI={10.1116/1.1305289}, abstractNote={Using a real-space multigrid method and ab initio pseudopotentials we calculated the reflectance anisotropy spectra for (001) growth structures of GaP and InP as well as for stepped Si(111):H and hydrogenated Si(110) surfaces. Our results, obtained within DFT-LDA, show good qualitative agreement with recent experiments. Further improvement is achieved by using a numerically efficient GW approach with approximations for local-field effects and dynamical screening. We find the contributions to the anisotropy signal related either directly to surface states or to transitions between surface-perturbed bulk wave functions. Our results demonstrate the high sensitivity of RAS to the surface structure and chemistry and show that the optical transitions causing the anisotropy signal take place mainly in a few uppermost atomic layers of the substrate.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Schmidt, WG and Bechstedt, F and Bernholc, J}, year={2000}, pages={2215–2223} }
 @article{schmidt_esser_frisch_vogt_bernholc_bechstedt_zorn_hannappel_visbeck_willig_et al._2000, title={Understanding reflectance anisotropy: Surface-state signatures and bulk-related features in the optical spectrum of InP(001)(2X4)}, volume={61}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.61.r16335}, abstractNote={A detailed analysis based on first-principlescalculations with self-energy corrections is combined with photoemission spectroscopy to determine the origin of features observed in reflectance anisotropy spectroscopy ~RAS! at semiconductor surfaces. Using the InP(001)(2 34) surface as a model case we obtain quantitative agreement between slab calculations and low-temperature RAS measurements. We find the contributions to the anisotropy signal related either directly to surface states or to transitions between surface perturbed bulk wave functions. Our results demonstrate the high sensitivity of RAS to the surface structure and chemistry and show that the absorption processes causing the anisotropy signal take place in the uppermost few atomic layers of the substrate.}, number={24}, journal={PHYSICAL REVIEW B}, author={Schmidt, WG and Esser, N and Frisch, AM and Vogt, P and Bernholc, J and Bechstedt, F and Zorn, M and Hannappel, T and Visbeck, S and Willig, F and et al.}, year={2000}, month={Jun}, pages={16335–16338} }
 @article{frisch_schmidt_bernholc_pristovsek_esser_richter_1999, title={(2x4) GaP(001) surface: Atomic structure and optical anisotropy}, volume={60}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.60.2488}, abstractNote={We have investigated the microscopic structure and optical anisotropy of $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstructed GaP(001) surfaces. Optical and electron spectroscopy from GaP(001) surfaces prepared in ultrahigh-vacuum conditions were combined with first-principles calculations of the energetics and reflectance anisotropy. Symmetry, composition and surface optical anisotropy were characterized by low-energy electron diffraction, Auger electron spectroscopy, photoemission spectroscopy and reflectance anisotropy spectroscopy. In contrast to most earlier reports, we find that the stable Ga-rich surface corresponds to a $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstruction. No $(4\ifmmode\times\else\texttimes\fi{}2)$ reconstruction could be observed, independent of the preparation method. Depending on the Ga coverage, however, two distinct line shapes in the reflection anisotropy spectra occur, indicating the existence of at least two different surface phases with $(2\ifmmode\times\else\texttimes\fi{}4)$ periodicity. This agrees with our total-energy calculations: Four $(2\ifmmode\times\else\texttimes\fi{}4)$ structural models may be stable depending on the chemical potentials of the surface constituents. All considered $(4\ifmmode\times\else\texttimes\fi{}2)$ structures, however, are unstable. Based on the comparison between calculated reflectance anisotropy spectra and measured data we suggest mixed Ga-P dimers on top of the Ga-terminated substrate as ground-state geometry for the cation-rich phase of GaP(001)$(2\ifmmode\times\else\texttimes\fi{}4)$. Our results indicate the formation of P dimers at the surface for the more anion-rich phase of GaP(001)$(2\ifmmode\times\else\texttimes\fi{}4)$.}, number={4}, journal={PHYSICAL REVIEW B}, author={Frisch, AM and Schmidt, WG and Bernholc, J and Pristovsek, M and Esser, N and Richter, W}, year={1999}, month={Jul}, pages={2488–2494} }
 @article{esser_schmidt_bernholc_frisch_vogt_zorn_pristovsek_richter_bechstedt_hannappel_et al._1999, title={GaP(001) and InP(001): Reflectance anisotropy and surface geometry}, volume={17}, ISSN={["1071-1023"]}, DOI={10.1116/1.590810}, abstractNote={We have investigated the optical anisotropy of GaP(001) and InP(001) surfaces. The samples were prepared by homoepitaxial metalorganic vapor phase epitaxy growth and either directly transferred into ultrahigh vacuum (UHV) or in situ capped and, after transfer, decapped in UHV by thermal desorption of a P/As capping layer. Symmetry, composition, and surface optical anisotropy were characterized by low-energy electron diffraction, Auger electron spectroscopy, and reflectance anisotropy spectroscopy. We observe (2×1)/(2×2)-like reconstructions for the very P-rich and (2×4) reconstructions for the more cation-rich surfaces. No (4×2) reconstruction could be prepared, independent of the preparation method. A comparison of the reflectance anisotropy between GaP(001) and InP(001) surfaces shows similar line shapes for the very cation-rich (2×4) surfaces. For less cation-rich surfaces, however, we observe distinct differences between the spectra of the two systems. In both cases, different line shapes in the reflection anisotropy spectra occur for the (2×4) periodicity, suggesting the existence of different (2×4) geometries. The experimental results are discussed on the background of atomic structures, total energies and reflectance anisotropy spectra obtained ab initio from density-functional theory local-density approximation calculations.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Esser, N and Schmidt, WG and Bernholc, J and Frisch, AM and Vogt, P and Zorn, M and Pristovsek, M and Richter, W and Bechstedt, F and Hannappel, T and et al.}, year={1999}, pages={1691–1696} }
 @article{schmidt_fattebert_bernholc_bechstedt_1999, title={Self-energy effects in the optical anisotropy of GaP(001)}, volume={6}, ISSN={["0218-625X"]}, DOI={10.1142/S0218625X99001281}, abstractNote={ We calculate the reflectance anisotropy for GaP(001)(2×4) surfaces using a real-space multigrid method and ab initio pseudopotentials. Our results obtained within DFT-LDA show good qualitative agreement with recent experiments. This holds in particular for the stoichiometric trends. A strong negative anisotropy at low photon energies is linked to the formation of Ga–Ga bonds along the [110] direction. There are discrepancies, however, with respect to the line shape and the energetic positions of characteristic peaks. Substantial improvement is achieved by using a numerically efficient GW approach with approximations for local-field effects and dynamical screening. We find that the spectral features related to transitions between surface perturbed bulk wave functions are more strongly affected by self-energy corrections than anisotropies directly linked to surface electronic states. }, number={6}, journal={SURFACE REVIEW AND LETTERS}, author={Schmidt, WG and Fattebert, JL and Bernholc, J and Bechstedt, F}, year={1999}, month={Dec}, pages={1159–1165} }
 @article{schmidt_briggs_bernholc_bechstedt_1999, title={Structural fingerprints in the reflectance anisotropy spectra of InP(001)(2x4) surfaces}, volume={59}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.59.2234}, abstractNote={The reflectance anisotropy has been calculated from first principles for a series of recently proposed structural models of the $\mathrm{InP}(001)(2\ifmmode\times\else\texttimes\fi{}4)$ surface. The features of the calculated spectra are related to specific surface bonding configurations. We find a pronounced negative anisotropy around 1.7 eV linked to transitions between \ensuremath{\sigma}-like In-In bonding states and empty dangling bonds localized at the surface cations. The strength of that anisotropy is directly related to the number of In-In bonds at the surface. This explains the gradual change of the corresponding measured anisotropy in that energy region, depending on the growth conditions. Positive anisotropies at higher energies arise from transitions between P-P dimer related states and surface resonances. Additionally we find derivativelike features at the energy of the ${E}_{1}$ peak that depend only weakly on the surface structure and stoichiometry. In conjunction with the experimental data, our results indicate that the (2\ifmmode\times\else\texttimes\fi{}4) reconstructed InP(001) surface features In-In bonds along [110] and P-P dimers parallel to $[11\ifmmode\bar\else\textasciimacron\fi{}0],$ respectively. The relative number of these bonds varies with the growth conditions.}, number={3}, journal={PHYSICAL REVIEW B}, author={Schmidt, WG and Briggs, EL and Bernholc, J and Bechstedt, F}, year={1999}, month={Jan}, pages={2234–2239} }
 @article{bechstedt_pulci_schmidt_1999, title={Theoretical aspects of the optical response of semiconductor surfaces}, volume={175}, ISSN={["1862-6319"]}, DOI={10.1002/(sici)1521-396x(199909)175:1<5::aid-pssa5>3.0.co;2-9}, abstractNote={We discuss the progress in realistic calculations of the optical response of semiconductor surfaces. It concerns numerical developments as well as the better inclusion of many-body effects. We show that the starting point of such calculations, the atomic structure and the surface equilibrium phase, can be now derived with high accuracy. The different steps are described in detail for the computation of the reflectance anisotropy and the exploration of the In-rich InP(001)2 4 surfaces.}, number={1}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Bechstedt, F and Pulci, O and Schmidt, WG}, year={1999}, month={Sep}, pages={5–16} }
 @article{schmidt_bechstedt_1998, title={Geometry and electronic structure of InP(001)(2 x 4) reconstructions}, volume={409}, ISSN={["1879-2758"]}, DOI={10.1016/S0039-6028(98)00260-X}, abstractNote={We investigate the atomic and electronic structure of the InP(001) surface by means of first-principles pseudopotential calculations within density-functional theory. We are able to rule out (4×2) reconstruction models as well as trimer configurations proposed recently as possible equilibrium structures. We predict (2×4) reconstructions characterized by asymmetric In–P or symmetric P dimers for an In-rich and a balanced surface stoichiometry, respectively. For a very limited range of preparation conditions we cannot exclude, however, the existence of further stable (2×4) reconstructions. All favourable equilibrium structures are characterized by filled and empty surface bands close to the bulk valence and conduction band edges, respectively. Details of the geometry and electronic properties for the various possible surface reconstructions are given and compared with the experimental data available.}, number={3}, journal={SURFACE SCIENCE}, author={Schmidt, WG and Bechstedt, F}, year={1998}, month={Jul}, pages={474–484} }