Predicting structural phase transition temperatures of halide perovskites from first-principles lattice dynamics*

All-inorganic halide perovskites CsBX₃ (B=Sn, Pb; X=Cl, Br, I) display successive structural phase transitions from high-temperature cubic phase to low-temperature phases. An accurate prediction of the structural phase transition temperature (T_s) from first principles is still challenging because lattice vibration is extremely anharmonic in CsBX₃, particularly near the structural phase transition temperature, for which the quasiharmonic theory completely fails. Moreover, the choice of the exchange-correlation functional sensitively affects the relative stability of the competing phases, leading to a significant variation in the predicted T_s values.

Here, to understand the best practices for the T_s prediction, we perform comprehensive ab initio lattice dynamics calculations on halide perovskites using the recently developed self-consistent phonon methods [1, 2]. We show that the predicted Ts value closely correlates with the lattice constants used. Also, we discuss how the Ts value changes when one employs a different level of anharmonic lattice dynamics method.