Zone-center phonons in yellow phase CsSnI3

Abstract

The zone-center phonons are calculated for yellow phase CsSnI3 using density functional perturbation theory in a plane-wave pseudopotential method. The infrared absorption and reflection spectra are simulated and show that the absorption has a strong contribution from the LO as well as TO modes. The polarization-dependent Raman spectra for various configurations are simulated. The results for the Raman and the infrared reflection spectra are found to be in good agreement with the available experimental data when averaging over directions. The Born effective charges and high- and low-frequency dielectric tensors are calculated. The ratio of the static to the high-frequency dielectric constants is high in the y direction.