Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session D15: Electronic Structure I |
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Sponsoring Units: DCOMP Chair: Victor Pardo, University of California, Davis Room: D171 |
Monday, March 21, 2011 2:30PM - 2:42PM |
D15.00001: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 2:42PM - 2:54PM |
D15.00002: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 2:54PM - 3:06PM |
D15.00003: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 3:06PM - 3:18PM |
D15.00004: Unfolding first-principles band structures Wei Ku, T. Berlijn, C.-C. Lee A general method [1] is presented to unfold band structures of first-principles supercell calculations with proper spectral weight, allowing easier visualization of the electronic structure and the degree of broken translational symmetry. The resulting unfolded band structures contain additional rich information from the Kohn-Sham orbitals, and absorb the structure factor that makes them ideal for a direct comparison with angle resolved photoemission spectroscopy experiments. With negligible computational expense via the use of Wannier functions, this simple method has great practical value in the studies of a wide range of materials containing impurities, vacancies, lattice distortions, or spontaneous long-range orders. \\[4pt] [1] Wei Ku, T. Berlijn, and C.-C. Lee, Phys. Rev. Lett. {\bf 104}, 216401 (2010). [Preview Abstract] |
Monday, March 21, 2011 3:18PM - 3:30PM |
D15.00005: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 3:30PM - 3:42PM |
D15.00006: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 3:42PM - 3:54PM |
D15.00007: Finite-basis correction applied to the optimized effective potential within the FLAPW method Christoph Friedrich, Markus Betzinger, Stefan Bl\"ugel The optimized-effective-potential (OEP) method is a special technique to construct local exchange-correlation (xc) potentials from general orbital-dependent xc energy functionals for density-functional theory. Recently, we showed that particular care must be taken to construct local potentials within the all-electron full-potential augmented-plane-wave (FLAPW) approach. In fact, we found that the LAPW basis had to be converged to an accuracy that was far beyond that in calculations using conventional functionals, leading to a very high computational cost. This could be traced back to the convergence behavior of the density response function: only a highly converged basis lends the density enough flexibility to react adequately to changes of the potential. In this work we derive a numerical correction for the response function, which vanishes in the limit of an infinite, complete basis. It is constructed in the atomic spheres from the response of the basis functions themselves to changes of the potential. We show that such a \textit{finite-basis correction} reduces the computational demand of OEP calculations considerably. We also discuss a similar correction scheme for $GW$ calculations. [Preview Abstract] |
Monday, March 21, 2011 3:54PM - 4:06PM |
D15.00008: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 4:06PM - 4:18PM |
D15.00009: ESTEST: A Framework for the Verification and Validation of Electronic Structure Codes Gary Yuan, Francois Gygi ESTEST is a verification and validation (V\&V) framework for electronic structure codes that supports Qbox, Quantum Espresso, ABINIT, the Exciting Code and plans support for many more. We discuss various approaches to the electronic structure V\&V problem implemented in ESTEST, that are related to parsing, formats, data management, search, comparison and analyses. Additionally, an early experiment in the distribution of V\&V ESTEST servers among the electronic structure community will be presented. [1] G. Yuan and F. Gygi, Computational Science and Discovery (2010) (in press). [Preview Abstract] |
Monday, March 21, 2011 4:18PM - 4:30PM |
D15.00010: The random phase approximation and beyond: an assessment for molecular binding energies and reaction barrier heights Xinguo Ren, Patrick Rinke, Matthias Scheffler, Joachim Paier, Andreas Gr{\"u}eneis, Georg Kresse, Gustavo E. Scuseria The random phase approximation (RPA) for the correlation energy has become a promising approach for describing electronic systems in various bonding situations. Recent efforts have focused mainly on correcting the general tendency of RPA to underestimate bond strengths e.g. by adding corrections from second-order screened exchange (SOSEX) [1,2] or single excitations (SE) [3]. In this work, we systematically assess the influence of SOSEX, SE and their combinations on the atomization energies of the G2-I molecular set, as well as the chemical reaction barrier heights of the HTBH38/04 and NHTBH38/04 benchmark sets [4]. We find that RPA+SOSEX+SE based on PBE gives the most balanced description. However, for reaction barrier heights standard RPA based on PBE turns out to be better and is surprisingly accurate. The underlying mechanism governing the performance of RPA and its variants in different circumstances will be analysed. [1] A. Gr\"uneis {\it et al.}, J. Chem. Phys. \textbf{131}, 154115 (2009). [2] J. Paier {\it et al.} J. Chem. Phys. \textbf{132}, 094103 (2010). [3] X. Ren {\it et al.}, arXiv:cond-mat/1011.2724. [4] Y. Zhao {\it et al.} J. Phys. Chem. A \textbf{109}, 2012 (2005) [Preview Abstract] |
Monday, March 21, 2011 4:30PM - 4:42PM |
D15.00011: Approximating Densities of States with Gaps Roger Haydock, C.M.M. Nex Reconstructing a density of states or similar distribution from moments or continued fractions is an important problem in calculating the electronic and vibrational structure of defective or non-crystalline solids. For single bands a quadratic boundary condition introduced previously [Phys. Rev. B 74, 205121 (2006)] produces results which compare favorably with maximum entropy and even give analytic continuations of Green functions to the unphysical sheet. In this paper, the previous boundary condition is generalized to an energy-independent condition for densities with multiple bands separated by gaps. As an example it is applied to a chain of atoms with s, p, and d bands of different widths with different gaps between them. The results are compared with maximum entropy for different levels of approximation. Generalized hypergeometric functions associated with multiple bands satisfy the new boundary condition exactly. [Preview Abstract] |
Monday, March 21, 2011 4:42PM - 4:54PM |
D15.00012: A New Boundary Condition for Embedding Atoms in Solids G.A. Benesh, Roger Haydock Previously, Haydock and Nex [Phys. Rev. B 82, 205114 (2010)] formulated an approximation for embedding a finite discrete system into an infinite substrate by means of a new boundary condition. This boundary condition requires a maximum breaking of time-reversal symmetry (MBTS) in the sense that probability is carried away from the embedding surface at a maximal rate. The MBTS boundary condition has been useful in discrete systems for constructing accurate densities of states and other distributions from moments or continued fractions. In this work, we generalize the approach to the problem of embedding an atom or a cluster of atoms into an infinite solid. The new, continuous MBTS boundary condition has been applied to model systems and to the embedding of a hydrogen atom. Results are presented and compared with other methods. [Preview Abstract] |
Monday, March 21, 2011 4:54PM - 5:06PM |
D15.00013: Reference Calculation of Temperature-dependent Behavior of Confined Many-electron Systems Frank E. Harris, Travis Sjostrom Confined many-electron systems at finite temperatures present a major challenge to density functional theory. Very little is known about the free energy behavior over the temperature range of interest, for example, in the study of warm dense matter, and as a result, it is difficult to assess the validity of proposed free energy density functionals. We present preliminary results on a comparatively simple but computationally feasible model, namely thermally occupied Hartree-Fock states for eight one-electron atoms in a box. We discuss the main technical task, evaluation of the required matrix elements, and summarize the results thus far obtained. [Preview Abstract] |
Monday, March 21, 2011 5:06PM - 5:18PM |
D15.00014: Finite-temperature Exchange and Correlation Functionals in Self-Consistent Calculations T. Sjostrom, V.V. Karasiev, S.B. Trickey Density functional theory is being used increasingly to investigate systems at substantial electron temperatures (e.g., warm dense matter, order of 1-10 eV or more). A common approach uses a ground-state (zero-temperature) exchange-correlation (XC) functional with thermal occupancy (Fermi distribution) of the Kohn-Sham states. Various finite-temperature extensions for XC free energy (Sommerfeld expansion, RPA, STLS, classical map) have been proposed, however. All have LDA form. We have implemented several in a pseudopotential code (SIESTA), and also extended them to have the PBE-GGA as the zero-temperature limit. We report equation of state calculations for Li from ambient density and temperature through the warm dense matter regime. Nontrivial variation is found. [Preview Abstract] |
Monday, March 21, 2011 5:18PM - 5:30PM |
D15.00015: Finite Temperature Scaling of the Non-interacting Free Energy Density Functional J.W. Dufty, V.V. Karasiev, S.B. Trickey The non-interacting free energy density functional is central to formulation of orbital-free DFT, yet its construction remains a challenge. Here, exact scaling relations and related bounds are obtained for guidance. First, that free energy is expressed as a functional of one-body reduced density operators that deliver the same average number density. For a one-component Fermion system, this functional has a minimum at the Fermi operator whose external potential assures the chosen number density. This is the formal definition of the non-interacting free energy density functional. The associated entropy and internal energy functionals are identified directly. A unitary transformation generating spatial scaling then determines how these functionals change under density scaling. As an application, these scaling laws are used to obtain inequalities and bounds for functionals at different values of the density and temperature. Relationships to similar recent work at finite temperatures, and the extensive prior zero-temperature results are noted. [Preview Abstract] |
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