Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 13: Elektronentheorie

HL 13.1: Talk

Monday, March 24, 2003, 16:00–16:15, BEY/118

Ground-state based formulation of the exact exchange (EXX) formalism — •Matthias Wahn and Jörg Neugebauer — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem, Germany

In order to describe the exchange-potential in density-functional theory the most common approximations are based on local LDA or GGA functionals. However, these functionals have well known deficiancies in describing band gaps or negative charged ions. Recent studies have shown that the exact treatment of the exchange-potential (EXX-method) within the Kohn-Sham formalism largely compensates these deficiencies [1]. The original formulation is based on a Greens function approach requiring the calculation of a large number of unoccupied states thus making the approach computationally rather expensive. We propose an alternative formulation of the EXX-method that bases on a variational principle and only requires as input ground state properties. The key idea is to calculate variational derivatives by using first-order perturbation-theory. Then, by using the Sternheimer-equation for the occupied states and constructing a variational energy functional the problem reduces to a simple minimizing problem. The method has been implemented for atoms and results for the closed-shell atoms beryllium and neon will be discussed.

[1] M. Städele, M. Moukara, J.A. Majewski, P. Vogl, and A. Görling, Phys. Rev. B, 59, 10031 (1999)