Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 7: Microstructures and Phase Transformations: Oxides & Perovskites

MM 7.2: Vortrag

Montag, 5. September 2022, 16:00–16:15, H45

Phase transitions and phonon renormalization in CsPbBr₃ via a machine learning interatomic potential — •Erik Fransson¹, Fredrik Eriksson¹, Petter Rosander¹, Terumasa Tadano², and Paul Erhart¹ — ¹Chalmers University of Technology, Gothenburg, Sweden — ²National Institute for Materials Science, Tsukuba, Japan

Here, we present a study on phase-transition and phonon renormalization in the metal halide perovskite CsPbBr₃ using a machine learning (ML) interatomic potential. The ML potential is a neuroevolution-potential constructed using the GPUMD software and is trained on atomic forces, energies and stresses obtained from DFT calculations. We find that the ML potential captures the correct phase-transition from the orthorhombic phase to tetragonal phase and from tetragonal to cubic phase. The phase transition temperatures obtained are slightly underestimated compared to experimental studies, but in good qualitative agreement. These phase-transitions are connected to the so called tilt-modes at the R and M point in the brillouin zone, which corresponds to tilting of the PbBr₆ octahedra. The dynamics of these modes are studied with MD simulations and mode projections, and we find that they have are strongly anaharmonic and over-damped character. Furthermore, we investigate and benchmark how different self-consistent phonon methods work for these strongly anharmonic modes.