Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 41: Methods in Computational Materials Modelling I: Ab initio thermodynamics

MM 41.2: Vortrag

Mittwoch, 9. März 2016, 16:00–16:15, H52

Ab initio description of phase transitions in pure Ti at finite temperatures — •Dominique Korbmacher, Albert Glensk, Blazej Grabowski, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany

Ti and its alloys play an important role in many industrial applications, for example in medicine or aircrafts. In this project we investigate pure Ti within a fully ab initio based methodology using density-functional theory and including anharmonicity. Because bcc Ti is dynamically unstable at lower temperatures standard approaches cannot be applied. We have therefore developed a new method (referred to as TU-TILD [1]) which allows to capture the anharmonic contribution also for unstable systems. This method is based on optimized interatomic potentials which can be used as a highly efficient reference for thermodynamic integration. Applying the TU-TILD methodology, we have accurately investigated the phase stabilities of the three relevant phases in Ti (ω, hcp and bcc). In particular we calculated the free energies and derived thermodynamic properties for the whole temperature regime up to the melting point, using two different exchange-correlation functionals. We show that the ω to hcp as well as the hcp to bcc phase transition are correctly predicted by our methods. Furthermore we discuss the second order bcc to ω phase transition.

[1] A. I. Duff, et al., PRB 91, 214311 (2015).