Regensburg 2019 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 8: Topical session (Symposium MM): High entropy and compositionally complex alloys
MM 8.3: Talk
Monday, April 1, 2019, 16:30–16:45, H43
Ab initio vibrational free energies including anharmonicity for multicomponent alloys — •Prashanth Srinivasan1, Yuji Ikeda2, Blazej Grabowski2, Jan Janssen2, Alexander Shapeev3, Jörg Neugebauer2, and Fritz Körmann1,2 — 1TU Delft — 2MPIE Dusseldorf — 3Skolkovo Institute of Science and Technology
High entropy alloys have gained widespread attention owing to their superior mechanical properties. Ab inito modeling is a powerful tool to analyze and predict their thermodynamic properties. In combination with statistical sampling techniques, free energy surfaces F(T,V) are accessible from which properties such as thermal expansion coefficient and heat capacity can be derived and compared to experiments. At higher temperatures, the vibrational free energy — including anharmonic contributions — is a major contributor. But as the number of components in the alloy increases, ab initio calculations to obtain accurate values of the free energy become expensive. In this work, we present an efficient approach to numerically calculate exact vibrational free energies. Firstly, a machine learnt potential (moment tensor potential [Shapeev, 2016]) is built based on ab initio data, the validity of which is tested by comparing its results to DFT, and secondly, the MTP is used as a part of a thermodynamic integration to get accurate vibrational free energies. The approach is applied to 12 refractory alloys having two to five components to study the impact of configurational entropy on the vibrational free energies. The workflow is implemented in pyiron (http://pyiron.org) to enhance its dissemination and reuse.