Berlin 2024 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 62: Developement of Calculation Methods III
MM 62.8: Talk
Thursday, March 21, 2024, 17:30–17:45, C 264
Ab initio Raman spectroscopy including temperature: Theory and application for GaN and BaZrS3 — •Florian Knoop1, Nimrod Benshalom2, Matan Menahem2, Omer Yaffe2, and Olle Hellman2 — 1Linköping University, Sweden — 2Weizmann Institute of Science, Israel
Ab initio simulations of Raman spectroscopy are often performed within the harmonic approximation, which is insufficient for describing realistic spectral properties of materials. Here we present a numerically efficient scheme that couples ab initio simulations, equivariant neural network potentials, and self-consistent phonon theory in the temperature-dependent effective potentials (TDEP) framework to perform precise simulations of Raman response at finite temperature. The method is presented for wurtzite GaN in comparison to latest experimental results, with a focus on rigorous treatment of direction and polarization-orientation (PO) dependence in optically anisotropic solids with LO/TO splitting, which is often neglected in computational approaches. Subsequently we discuss BaZrS3, a highly polarizable yet lead-free chalcogenide Perovskite with strong optical response to showcase the approach for complex materials. Overall, we find excellent agreement with experiment for both materials and show how the polarization information can be used e.g. to discern crystallographic orientations. We conclude by discussing limits and systematic errors in the approach with implications for other materials simulations, as well as possible strategies to overcome some of them by tighter integration of experiment and theory.