Contrasting GGA and hybrid functionals description of dynamic properties of CsPbI₃

Caesium lead iodide perovskite exhibit similar structural properties than methylammonium (MA) lead iodide, in particular with respect to the inorganic cage. Both systems show anharmonic behavior in the halide dynamics. Having Cs instead of MA as the cation allows for a study based on expensive hybrid functionals. Considering that most of the reported first principles molecular dynamics simulations were performed using GGA functionals, it becomes pertinent to question what are the corresponding results when the forces are accounted for using the more accurate hybrid functionals. In this work we present a comparison between PBE and HSE functionals for the anharmonicity of the halide atoms at high temperature. Our study is based on first principles molecular dynamics simulations on large 444 supercells and trajectories extending up to 40 ps.