Study of phase transition, structural stability and mechanical properties of CsPbBr3 under high pressure by first principles

The perovskite material CsPbBr3 possesses a large effective tolerance factor, good structural stability, high carrier mobility, and high photoelectric conversion efficiency, making it a promising candidate for solar cell materials. Its photoelectric properties depend on the composition, morphology, and structure of the crystal. Pressure is a crucial factor that influences the crystal structure. This study employs density functional theory (DFT) to investigate the conditions for pressure-induced phase transitions in CsPbBr3 and the effect of pressure on its structural stability and mechanical properties. The results indicate that CsPbBr3 transitions from the Cmcm phase to the P4/mbm phase at 0.03 GPa; from Pm3m to Pnma at 0.33 GPa; from Cmcm to Pnma at 0.024 GPa; from P4/ mbm to I4/mcm at 0.015 GPa; and from a non-perovskite to a perovskite structure within the same Pnma space group at 0.0065 GPa. Additionally, the N-Pnma phase transitions to the I4/mcm phase at 0.006 GPa; the Cmcm phase transitions to I4/mcm at 0.02 GPa; the Pm3m phase transitions to I4/mcm at 0.2 GPa; and the N-Pnma phase transitions to P4/mbm at 0.0036 GPa, and the P4/mbm phase transitions to Pnma at 0.018 GPa. Among all crystal phases of CsPbBr3, the Cmcm phase exhibits the best ductility under normal pressure, the Pm3m phase shows the highest stiffness at 0.33 GPa, and the Cmcm phase displays the greatest plasticity at 0.03 GPa. This work provides a theoretical foundation for understanding the phase transition conditions of perovskite CsPbBr3 and the effects of pressure on its mechanical properties.