Temperature-driven structural phase transitions in CsPbBr3

CsPbBr3 possesses soft lattices that, when heated, go through temperature-driven solid-solid phase transitions. By examining Gibbs free energies determined by lattice dynamics simulation, integrating both quasi-harmonic phonons and quasi-anharmonic phonons, this study explores the polymorph stabilities and phase transitions in CsPbBr3. The existence of any additional polymorphs, which are frequent in other metal halide perovskites, was ruled out in CsPbBr3, and three well-known phase transitions (orthorhombic (Pnma) to tetragonal (P4/mbm), then to cubic (Pm3m)) were successfully replicated. It has been found that the quasi harmonic approximation QHA, accurately predicts the phase transitions in CsPbBr3. When anharmonicity is introduced, the Gibbs free energy lowers, demonstrating that the intrinsic anharmonicity of the high temperature cubic phase is what gives it its stability. The impact of temperature from the point at which symmetry breaks to the melting point is discussed and investigated.