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M: Metallphysik

M 16: Phasenumwandlung I

M 16.5: Vortrag

Samstag, 5. März 2005, 10:15–10:30, TU H1058

Ab initio based free energy surfaces: A powerful tool to derive temperature dependent thermodynamic and kinetic parameters — •Blazej Grabowski — Uni Paderborn

Blazej Grabowski, Sixten Boeck, Jörg Neugebauer Uni Paderborn MPI für Eisenforschung Düsseldorf

Many metals and alloys exhibit a complex pressure and temperature dependent phase diagram. The common approaches to theoretically predict these diagrams are based on empirical interpolation schemes in connection with experimental input data. The ab initio calculation of free energy surfaces as function of relevant reaction coordinates (e.g. lattice constant, c/a ratio) provides a direct tool to identify stable and metastable equilibrium configurations, reaction barriers and reaction pathes by fully including temperature effects. In order to test the applicability and accuaracy of this approach we have implemented an efficient scheme in our plane wave pseudopotential code (SFHIngX) to calculate free energy surfaces employing the quasi harmonic approximation. The method has been applied to map the free energy surface of several metals (Al, Fe). The results are compared with experiment.