Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Computational Materials Modelling: Materials at finite temperatures

MM 5.1: Vortrag

Montag, 20. März 2017, 10:15–10:30, IFW B

Accurate electronic free energies of the transition metals at high temperatures — •Xi Zhang¹, Blazej Grabowski¹, Fritz Körmann^1,2, Christoph Freysoldt¹, and Jörg Neugebauer¹ — ¹Max-Planck-Institut für Eisenforschung GmbH, D-40237, Düsseldorf, Germany — ²Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, Netherlands

Free energies of bulk materials are nowadays routinely computed by density functional theory. In particular for metals, electronic excitations can significantly contribute to the free energy. Neglecting non-adiabatic contributions, electronic free energies can be obtained at relatively low computational cost, e.g., from the electronic density of states (DOS) at T=0 K or by utilizing the Sommerfeld approximation. However, the actual error introduced by such approximations and the electron-phonon coupling effect at elevated temperatures is rarely known, even though it could affect, e.g., theoretical phase stability predictions. In order to clarify these issues we have computed the electronic free energies for all 3d, 4d, and 5d transition elements in the bcc, fcc, and hcp structures. For selected elements we have performed ab initio molecular dynamic simulations to investigate the electron-phonon coupling effect. We provide an analysis of the observed chemical trends in terms of the electronic DOS and the canonical d band model. The error in the approximate methods as well as the specific validity ranges for their application are clarified. The electronic heat capacities of all investigated elements as well as the error analysis within the Sommerfeld model are also presented.