Dresden 2009 – wissenschaftliches Programm

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SYAI: Symposium Ab-Initio Approaches to Excitations in Condensed Matter

SYAI 1: Invited Talks

SYAI 1.1: Hauptvortrag

Donnerstag, 26. März 2009, 15:00–15:30, SCH 251

Insights and Progress in Density Functional Theory — Paula Paula Mori-Sanchez, Aron Cohen, and •Weitao Yang — Department of Chemistry, Duke University

Density functional theory of electronic structure is widely and successfully applied in simulations throughout engineering and sciences. However, there are spectacular failures for many predicted properties, which can be traced to the delocalization error and static correlation error of commonly used approximations. These errors include underestimation of the barriers of chemical reactions, the band gaps of materials, the energies of dissociating molecular ions and charge transfer excitation energies. Typical DFT calculations also fail to describe degenerate or near degenerate systems, as arise in the breaking of chemical bonds, and strongly correlated materials. These can all be characterized and understood through the perspective of fractional charges and fractional spins introduced recently. The failure to describe the bandgaps in Mott insulators can also be traced to the violation of the combined condition for fractional charges and fractional spins. Understanding the errors of functionals in the simplest way possible --- as violations of exact conditions for fractional charges and fractional spins -- opens the path forward for reduction of the errors and for applications of density functional theory in new frontiers. [P. Mori-Sanchez, A. J. Cohen, and W. T. Yang, Phys. Rev. Lett. 100:146401(2008); Phys. Rev. B,77:115123(2008); J. Chem. Phys. 129:121104(2008); Science, 321:792(2008); arXiv:0809.5108]