Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 33: Symposium Materials Modelling II

MM 33.3: Talk

Thursday, March 30, 2006, 15:30–15:45, IFW A

Ab initio calculation of thermodynamic properties of metals: xc-related error bars and chemical trends — •Blazej Grabowski, Tilmann Hickel, Sixten Boeck, and Jörg Neugebauer — Max-Planck Institut für Eisenforschung, Max-Planck Str. 1, 40237 Düsseldorf

Phase diagrams are indispensable tools in predicting material evolution during its processing. Current approaches to obtain such phase diagrams (e.g. CALPHAD) are based on extra- and interpolation of experimental data. Experimental costs and unreachability of metastable phases needed for these methods necessitate ab initio calculations without experimental input.

The accuracy of density-functional based ab initio methods is, in principle, only limited by the exchange-correlation functional. We have therefore evaluated the accuracy of the most commonly used functionals (LDA, PBE-GGA) by calculating key thermodynamic properties for a wide range of metallic materials (Fe, Al, Cu, Rh, Li, etc.). In particular, we have calculated the volume dependence of the free energy employing the quasiharmonic approximation. Great care was taken to ensure sufficient convergence with respect to supercell size, k-point sampling, and energy cutoff. Based on these results, we have derived thermodynamic quantities such as the thermal expansion coefficient and the temperature dependence of the free energy, which yield a direct insight into the quality of LDA and GGA for the various metals when compared to experimental data.