Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 18: Poster Session 2
MM 18.2: Poster
Dienstag, 6. September 2022, 17:30–20:00, P2
hiphive - Constructing and sampling higher order force constants for strongly anharmonic materials — •Erik Fransson1, Fredrik Eriksson1, Joakim Brorsson1, Zheyong Fan2, and Paul Erhart1 — 1Chalmers University of Technology, Gothenburg, Sweden — 2Aalto, University Helsinki Finland
Higher order force constants (FCs) play a key role in lattice dynamics and are crucial for the analysis of many thermodynamic materials properties. Typically FCs have been extracted using the finite displacement method, which suffers, however, from poor scaling with order and system size. In this contribution we present updates to and applications of the python package hiphive, a tool that allows the efficient extraction of FCs via a regression approach, both up to high order and for low symmetry systems. Higher order FCs can be used to directly run molecular dynamics (MD) simulations, however for strong anharmonic materials these models can become unstable. To overcome this obstacle, we present a self-consistent (iterative) approach for training higher order FCs and demonstrate its effectiveness for multiple strongly anharmonic materials. We have furthermore interfaced hiphive with the GPUMD software, which enables large scale molecular dynamics simulations using FC expansion potentials. This allows for sampling of, e.g., thermal conductivity via Green-Kubo techniques. This approach of extracting higher order FCs and sampling thermal conductivity is demonstrated for two very anharmonic materials, SnSe and BaGaGe. Lastly, we also demonstrate the application of this approach to study the complex dynamics of inorganic halide perovskites.