Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session D1: Fundamental Developments in Density Functional Theory |
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Sponsoring Units: DCOMP Chair: Neepa Maitra, Hunter College of the City University of New York Room: Morial Convention Center LaLouisiane AB |
Monday, March 10, 2008 2:30PM - 3:06PM |
D1.00001: Nearsightedness in Density Functional Theory Invited Speaker: |
Monday, March 10, 2008 3:06PM - 3:42PM |
D1.00002: Density-functional theory of superconductivity Invited Speaker: A prominent challenge of modern condensed-matter theory is to predict reliably material-specific properties of superconductors, such as the critical temperature. The traditional model of Bardeen, Cooper and Schrieffer (BCS) properly describes the universal features that all conventional superconductors have in common, but it is not able to make accurate predictions of material-specific properties. To tackle this problem, a density-functional formalism has been developed [1] which describes superconductors in thermal equilibrium in terms of three quantities: the ordinary density, the superconducting order parameter, and the nuclear N-body density. These three ``densities'' are determined self-consistently through a set of Kohn-Sham equations. Approximations of the universal exchange-correlation functional are derived on the basis of many-body perturbation theory. In this way, a true ab-initio description is achieved which does not contain any adjustable parameters such as the $\mu $* of Eliashberg theory. Numerical results for the critical temperature, the isotope effect, the gap function and the jump of the specific heat will be presented for simple metals, for MgB$_{2 }$[2] and CaBeSi, and for calcium intercalated graphite (CaC$_{6})$ [3]. Furthermore, results for Li, Al, K, and H under pressure will be discussed. The calculations explain why Li and Al behave very differently, leading to a strong enhancement of superconductivity for Li and to a clear suppression for Al with increasing pressure [4]. For K we predict a behavior similar to Li, i.e. a strong increase of T$_{c}$ with increasing pressure. Finally, hydrogen is found to be a three-gap superconductor whose critical temperature increases with increasing pressure until about 100K (at 500 GPa). \\ \noindent [1] M. L\"{u}ders, M.A.L. Marques, N.N. Lathiotakis, A. Floris,G. Profeta, L. Fast, A.Continenza, S. Massidda, E.K.U. Gross, PRB \underline {\textbf{72}}, 024545 (2005). \\ \noindent [2] A. Floris, G. Profeta, N.N. Lathiotakis, M. L\"{u}ders, M.A.L. Marques, C. Franchini, E.K.U. Gross, A. Continenza, S. Massidda, PRL \underline {\textbf{94}}, 037004 (2005). \\ \noindent [3] A. Sanna, G. Profeta, A. Floris, A. Marini, E.K.U. Gross, S. Massidda, PRB (Rapid Comm.) \underline {\textbf{75}}, 020511 (2007). \\ \noindent [4] G. Profeta, C. Franchini, N.N. Lathiotakis, A. Floris, A. Sanna, M.A.L. Marques, M. L\"{u}ders, S. Massidda, E.K.U. Gross, A. Continenza, PRL \underline {\textbf{96}}, 047003 (2006). [Preview Abstract] |
Monday, March 10, 2008 3:42PM - 4:18PM |
D1.00003: Remarks on Molecular Density Functional Theory Invited Speaker: The dft of finite molecular systems possesses unique special characteristics that produce challenges not yet met and promises not yet realized. I describe several of the problems in this subject with which we have been struggling. [Preview Abstract] |
Monday, March 10, 2008 4:18PM - 4:54PM |
D1.00004: The Partition Problem; Insights from Density Functional Theory Invited Speaker: How to partition a system into its components, the atoms in molecules problem and its multi-atomic generalizations, arises ubiquitously in physics, chemistry, and materials science. It is central to population analysis, chemical reactivity theory, issues of transferability, and relevant to computational methods for very large systems such as QM-MM and O(N) schemes. At issue is the decomposition of the total electron density into contributions from each part, whence the relevance of density functional theory. My collaborators and I have developed a new, exact scheme, partition theory, for that decomposition. It is based on the Perdew, Parr, Levy, and Balduz ensemble formulation of density functional theory. In this talk, the elements of partition theory will be described, including its formal structure, a dynamical version for efficient computation, and quantitative illustrations of its central features via the partition of very simple systems. [Preview Abstract] |
Monday, March 10, 2008 4:54PM - 5:30PM |
D1.00005: Restoring the Density-Gradient Expansion for Exchange in a GGA for Solid and Surfaces Invited Speaker: Density functionals for the exchange-correlation energy of a many-electron system are widely used in condensed-matter physics. Successful modern generalized gradient approximations (GGA's), developed largely for quantum chemistry, are biased toward free-atom energies. Recent ``GGA's for solids'' include PBEsol [1], a revised Perdew-Burke-Ernzerhof (PBE) GGA that improves equilibrium properties of densely-packed solids and their surfaces by recovering the first-principles density-gradient expansion for the exchange energy [2]. Results will be reported for the lattice constants of 20 solids and for the surface energy of jellium in the local spin density approximation and in the PBE and PBEsol GGA's. Other possible applications of PBEsol will be discussed. It will be argued (as in Ref. [3]) that the second-order gradient expansion is nearly converged for exchange, but not for correlation, in valence regions of typical solids (while atoms require a larger gradient coefficient for exchange). \newline [1] J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, K. Burke, http://arxiv.org/abs/0711.0156 \newline [2] P.R. Antoniewicz and L. Kleinman, Phys. Rev. B \textbf{31}, 6779 (1985). \newline [3] J.P. Perdew, L.A. Constantin, E. Sagvolden, and K. Burke, Phys. Rev. Lett. \textbf{97}, 223002 (2006). [Preview Abstract] |
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