| About this Abstract |
| Meeting |
2020 TMS Annual Meeting & Exhibition
|
| Symposium
|
Computational Thermodynamics and Kinetics
|
| Presentation Title |
Free Energy Calculation of Mechanically Unstable but Dynamically Stabilized Phases |
| Author(s) |
Sara Kadkhodaei, Axel van de Walle |
| On-Site Speaker (Planned) |
Sara Kadkhodaei |
| Abstract Scope |
The phase diagram of numerous materials of technological importance features high-symmetry high temperature phases that exhibit phonon instabilities. Leading examples include shape-memory alloys, as well as ferroelectric, refractory, and structural materials. The thermodynamics of these phases have proven challenging to handle by first-principles computational techniques due to the occurrence of constant anharmonicity-driven hopping between local low-symmetry distortions, while the system maintains a high-symmetry time-averaged structure. We present a novel method that efficiently explores the system’s ab-initio energy surface
by discrete sampling of local minima, which is combined with a continuous sampling of the vicinity of these local minima via a constrained harmonic lattice dynamic approach. The calculated free energies for the austenite and martensite phases in NiTi and PtTi shape memory alloys are presented. Finally, we introduce an open-access and fully automated software toolkit of the presented method. |
| Proceedings Inclusion? |
Planned: Supplemental Proceedings volume |