Effective phonons for finite-temperature Raman spectroscopy from first principles: GaN and BaZrS3

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• Dr. Florian Knoop, Linköping University
• Monday 10 June 2024, 14:30-15:00
• Zoom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHptUXlRSkppQT09.

If you have a question about this talk, please contact Dr Philipp Pracht.

Ab initio simulations of Raman spectroscopy are often performed within the harmonic approximation, which is insufficient for describing spectral properties of materials at realistic conditions. 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 [1, 2, 3]. The method is presented for wurtzite GaN in comparison to latest experimental results, with a focus on the rigorous treatment of direction and polarization-orientation (PO) dependence in optically anisotropic solids, which is crucial to discern crystallographic orientations and enable mode assignment. We discuss the importance of the interplay between harmonic dispersive properties and anharmonic interaction strength for properties primarily attributed to anharmonicity, such as linewidth broadening and thermal conductivity [4, 5, 6]. We subsequently apply the developed approach to a complex material, the highly polarizable yet lead-free chalcogenide Perovskite BaZrS3, and discuss how Raman spectroscopy and phonon theory can help to shed light on the microscopic mechanisms influencing its optoelectronic performance [7].

[1] FK et al., J. Open Source Softw 9, 6150 (2024); https://tdep-developers.github.io/tdep/ [2] MF Langer, JT Frank, FK, J. Chem. Phys. 159, 174105 (2023) [3] N Benshalom, et al., Phys Rev Mater 6, 033607 (2022) [4] FK, et al., Phys Rev Mater 4, 083809 (2020) [5] AH Romero et al., Phys Rev B 91 , 214310 (2015) [6] FK, et al., Phys Rev Lett 130, 236301 (2023) [7] K Ye, M Menahem, T Salzillo, FK, et al., arXiv 2402.18957

This talk is part of the Lennard-Jones Centre series.

This talk is included in these lists:

• Hanchen DaDaDash
• Lennard-Jones Centre
• Zoom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHptUXlRSkppQT09

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