@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{ramamoorthy_briggs_bernholc_1999, title={Chemical and strain effects on Boron-doped Si(100)}, volume={59}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.59.4813}, abstractNote={Theoretical investigations uncover complex strain-induced modes of boron ordering at the Si(100) surface, which are highly anomalous in comparison with other group III impurities. The fundamental units of the clustering process are subsurface pairs of B atoms. The structural relaxations around segregated B impurities are substantial and the induced strain fields couple with the $(2\ifmmode\times\else\texttimes\fi{}1)$ dimer reconstruction of the surface to stabilize complex, zigzag modes of ordering. Impurity configurations exist that are strongly bound with respect to isolated subsurface impurity pairs up to the critical doping level of 0.5 monolayer. Above this doping level, however, all modes of ordering of the impurities at the surface are repulsive. A number of experimental observations are explained and interesting structures are predicted.}, number={7}, journal={PHYSICAL REVIEW B}, author={Ramamoorthy, M and Briggs, EL and Bernholc, J}, year={1999}, month={Feb}, pages={4813–4821} }
 @article{ramamoorthy_briggs_bernholc_1999, title={Defect energetics and impurity incorporation mechanisms at the arsenic-passivated Si(100) surface}, volume={60}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.60.8178}, abstractNote={Theoretical calculations show that defect properties of the Si~100! and Si~100!:As surfaces are completely different. Large atomic relaxations around vacancies near the Si~100! surface cause chemical rebonding and defect healing that greatly lowers their formation energies. However, passivation of the surface by a monolayer of As induces substantial structural rigidity in the near-surface region. This reduces atomic relaxations and raises vacancy formation energies to high values, inhibiting vacancy mediated processes near the surface. The formation energies of silicon interstitials near the As-passivated surface are significantly lower than those of vacancies, which favors an interstitial mode of arsenic incorporation into the bulk during in diffusion. These results explain the observed uniformity of the Si~100!:As surface and the high level of electrical activation of in-diffused As. @S0163-1829~99!00835-8#}, number={11}, journal={PHYSICAL REVIEW B}, author={Ramamoorthy, M and Briggs, EL and Bernholc, J}, year={1999}, month={Sep}, pages={8178–8184} }
 @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{ramamoorthy_briggs_bernholc_1998, title={Chemical trends in impurity incorporation into Si(100)}, volume={81}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.81.1642}, abstractNote={Theoretical investigations of the adsorption, incorporation, and segregation of a number of common impurities at the (2 3 1)-Si(100) surface reveal two qualitatively distinct classes of behavior. Some impurities prefer to adsorb in trenches between surface dimer rows. Their incorporation into the surface is highly unfavorable. Other impurities prefer to adsorb on top of surface dimer rows. Their incorporation into the surface is either energetically favorable or only marginally unfavorable. The results explain a number of experimental observations. [S0031-9007(98)06884-7]}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Ramamoorthy, M and Briggs, EL and Bernholc, J}, year={1998}, month={Aug}, pages={1642–1645} }
 @article{bernholc_briggs_sullivan_brabec_nardelli_rapcewicz_roland_wensell_1997, title={Real space multigrid methods for large scale electronic structure problems}, volume={65}, DOI={10.1002/(SICI)1097-461X(1997)65:5<531::AID-QUA18>3.0.CO;2-5}, abstractNote={We describe the development and applications of a new electronic structure method that uses a real-space grid as a basis. Multigrid techniques provide preconditioning and convergence acceleration at all length scales and therefore lead to particularly efficient algorithms. The salient points of our implementation include: (i) new compact discretization schemes in real space for systems with cubic, orthorhombic, and hexagonal symmetry and (ii) new multilevel algorithms for the iterative solution of Kohn–Sham and Poisson equations. The accuracy of the discretizations was tested by direct comparison with plane-wave calculations, when possible, and the results were in excellent agreement in all cases. These techniques are very suitable for use on massively parallel computers and in O(N) methods. Tests on the Cray-T3D have shown nearly linear scaling of the execution time up to the maximum number of processors (512). The above methodology was tested on a large number of systems, such as the C60 molecule, diamond, Si and GaN supercells, and quantum molecular dynamics simulations for Si. Large-scale applications include a simulation of surface melting of Si and investigations of electronic and structural properties of surfaces, interfaces, and biomolecules. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 531–543, 1997}, number={5}, journal={International Journal of Quantum Chemistry}, author={Bernholc, Jerzy and Briggs, E. L. and Sullivan, D. J. and Brabec, C. J. and Nardelli, M. B. and Rapcewicz, K. and Roland, C. and Wensell, M.}, year={1997}, pages={531–543} }
 @article{boguslawski_briggs_bernholc_1995, title={NATIVE DEFECTS IN GALLIUM NITRIDE}, volume={51}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.51.17255}, abstractNote={The results of an extensive theoretical study of native defects in hexagonal GaN are presented. We have considered cation and anion vacancies, antisites, and interstitials. The computations were carried out using ab initio molecular dynamics in supercells containing 72 atoms. N vacancy introduces a shallow donor level, and may be responsible for the n-type character of as-grown GaN. Due to the wide gap of nitrides, self-compensation effects strongly reduce both n-type and p-type doping efficiencies due to the formation of gallium vacancy and interstitial Ga, respectively.}, number={23}, journal={PHYSICAL REVIEW B}, author={BOGUSLAWSKI, P and BRIGGS, EL and BERNHOLC, J}, year={1995}, month={Jun}, pages={17255–17258} }