Berlin 2024 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Phase Transformations II
MM 15.2: Vortrag
Montag, 18. März 2024, 17:00–17:15, C 230
Unusual spectral features in BaZrO3 — •Petter Rosander, Erik Fransson, Nicklas Österbacka, Paul Erhart, and Göran Wahnström — Chalmers university of technology, Gothenburg, Sweden
Barium zirconate BaZrO3 is one of few perovskites that retains an average cubic structure down to 0 K at ambient pressure. Despite this, it shows unusually sharp features in the Raman spectrum, which are supposed to be absent in a cubic system. In addition, a sharp reflection in electron diffraction appears at the R-point of the crystal at low temperatures. It has been suggested that these features are due to that the local structure of BaZrO3 may form nanodomains or a glass-like phase at low temperatures.
Here, the static structure factor of BaZrO3 is calculated as a function of temperature and pressure via molecular dynamics simulations using a machine-learned potential with near density functional theory (DFT) accuracy. A dielectric tensor model is also trained with near DFT accuracy to calculate the Raman spectrum as a function of pressure using molecular dynamics simulations.
We show that the sharp features in the Raman spectrum is due to higher order scattering and that the sharp reflection observed in electron diffraction is diffuse superlattice reflections that stems from the onset of a phase transition that never occurs.
Keywords: Phonons; Raman; Dynamical structure factor; Static structure factor; Anharmonicity