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MM: Fachverband Metall- und Materialphysik

MM 50: Computational Materials Modelling - Defects & Interfaces I

MM 50.3: Vortrag

Donnerstag, 14. März 2013, 10:45–11:00, H24

Effect of exchange-correlation functionals on vacancy formation energies — •Roman Nazarov, Tilmann Hickel, and Joerg Neugebauer — Max-Planck-Institut fuer Eisenforschung, Duesseldorf, Germany

The key quantity that determines vacancy concentration is the vacancy formation energy. Even small uncertainties in the vacancy formation energy lead to a deviation of the vacancy concentration by several orders of magnitude. In order to analyze the performance of various exchange-correlation functionals (LDA, PBE, PW91, and AM05) in density functional theory, we calculated vacancy formation energies for 12 fcc metals [1]. The obtained results show that generally the calculated vacancy formation energies are lower than the experimental ones. Furthermore, LDA based values are systematically higher, while the PW91 are systematically lower than the PBE vacancy formation energies. A careful analysis of the possible reasons for such results shows that discrepancies between the theoretical result and experiment as well as differences between theoretical values are mainly related to the way the various exchange-correlation functionals describe the internal surface of the vacancy. Based on this insight we propose an improved correction scheme which when postprocessing the DFT results yields a perfect alignment of vacancy formation energies for all exchange-correlation functionals. These corrected values are also in very good agreement with the experimental vacancy formation energies.

[1] R. Nazarov, T. Hickel, and J. Neugebauer, Phys. Rev. B 85, 144118 (2012)