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HL: Fachverband Halbleiterphysik

HL 13: Theory of electronic structure

HL 13.5: Vortrag

Montag, 25. Februar 2008, 17:15–17:30, EW 202

First-Principles Calculations of Electronic and Optical Properties of MnO and NiO — •Claudia Rödl, Frank Fuchs, Jürgen Furthmüller, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik and European Theoretical Spectroscopy Facility (ETSF), Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

The treatment of the antiferromagnetic transition-metal oxides within many-body perturbation theory (MBPT) remains a challenge. It is well-known for years that density-functional theory (DFT) in the local-density (LDA) and generalized-gradient approximation (GGA) yields very small or even negative gaps for this class of materials. Consequently, quasiparticle calculations using Hedin’s GW approximation in the commonly applied one-shot approach underestimate the fundamental gap significantly. That is why we use the non-local HSE03 exchange-correlation functional to obtain a reasonable starting point for a quasiparticle calculation within first-order perturbation theory. We explicitly focus on the compounds MnO and NiO which are usually considered as paradigmatic examples. Furthermore, we examine the optical properties of these materials. We solve the spin-polarized Bethe-Salpeter equation (BSE) and calculate optical absorption spectra including excitonic and local-field effects. In order to keep the computational demand treatable, we utilize the comparably less expensive GGA+U scheme for the subjacent electronic structure calculation.