Modeling of structure and phase transitions in CsPb(I1-xBrx)3 using a DFT-parameterized transferable force field

Inorganic lead halide perovskites, CsPbX3 (X = I and Br), have attracted considerable attention in the scientific community for their improved thermal stability compared to their hybrid counterparts and for their use in highly efficient solar cells. The mixed halide compositions CsPb(I1-xBrx)3 are widely used to tune optoelectronic properties while improving phase stability by suppressing the transformation of the photoactive black γ phase into the non-perovskite, photo-inactive yellow δ phase. Despite these advantages, no transferable classical force fields within a rigid-ion framework reliably describe both pure and mixed-halide systems. We report here a transferable force field comprising Lennard-Jones and Coulomb terms for inorganic lead halides CsPb(I1-xBrx)3. The force field is trained against density functional theory-computed energy-volume equations of state over a wide range of structural deformations. The developed force field is benchmarked by reproducing structural and mechanical properties, pressure dependent structural behavior, and temperature-driven phase transitions for the pure and mixed halide perovskites. These results demonstrate the transferability and robustness of the proposed force field for large-scale simulations of halide perovskites.