First-principles study of structural phase transition and thermal transport in halide perovskite CsPbBr₃

Halide perovskites have attracted significant attention in recent years for their excellent optoelectronic properties. While the optoelectronic properties of halide perovskites have been widely studied both experimentally and theoretically, their thermal properties have been studied only partially. In particular, first-principles study of phonon transport in halide perovskites is challenging because of the presence of unstable soft modes within the harmonic approximation.
In this study, we applied the recently developed self-consistent phonon (SCP) scheme [1] to investigate the three different phases of all-inorganic perovskite CsPbBr_3, and calculated the thermal conductivity κ_L and vibrational free energy from first principles. The SCP theory incorporates the anharmonic effect non-perturbatively and enables us to obtain well-defined phonons of the high-temperature phases. Also, we predicted the structural phase-transition temperatures T_c of CsPbBr₃ by comparing the anharmonic free-energy of the three phases. We will demonstrate the validity of our approach by comparing the predicted κ_L and T_c values with available experimental data and discuss the origin of the low κ_L.
[1] T. Tadano and S. Tsuneyuki, Phys. Rev. B 92, 054301 (2015); J. Phys. Soc. Jpn. 87, 041015 (2018).