Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 78: Frontiers of Electronic Structure Theory: Many-Body Effects on the Nano-Scale V

O 78.6: Talk

Thursday, March 19, 2015, 12:00–12:15, MA 004

Starting-point dependence in the Bethe-Salpeter equation: example of rutile TiO₂ — •Olga Turkina, Ute Werner, Dmitrii Nabok, and Claudia Draxl — Physics Department and IRIS Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, D-12489 Berlin, Germany

Many-body perturbation theory, combining the GW approach and the Bethe-Salpeter equation (BSE), is a powerful tool for the description of one- and two-particle excitations. However, employing density functional theory as a starting point for these methods may lead to results that depend on the choice of the exchange-correlation (xc) functional. This starting-point dependence is well known for the G₀W₀ approximation. Such dependence is expected to occur also for BSE calculations, however, has not yet been investigated. With the example of rutile TiO₂, we show that this is, indeed, the case. We employ two different xc functionals: the generalized gradient approximation (PBE) and a hybrid functional (PBE0’), combining a fraction of 25% exact exchange with PBE. The electronic structure is calculated using the G₀W₀ approximation. The BSE is solved to obtain the optical absorption spectra. These are analyzed with regard to the influence of eigenvalues, wave functions, and screening as originating from different xc functionals.