Charge redistribution induced surface stress for CsPbI 3 inorganic perovskite

Abstract The CsPbI 3 inorganic perovskite has high photovoltaic conversion efficiency and is a promising candidate for next-generation optoelectronic and energy-related technologies, but its application is seriously limited by low stability caused by surfaces and mechanical stresses. The surface stress may have strong effects on the stability of CsPbI 3 , but this quantity has so far not been well studied. In this work, the surface stress is systematically investigated for the CsPbI 3 with different surface orientations at different temperatures, by molecular dynamics simulations with the reactive force field potential. It is found that the surface stress can be as large as -0.2 GPa and 0.12 GPa along these two in-plane directions within the (100) surface, which is attributed to the surface-induced periodic pattern in the charge distribution. The anisotropic periodic charge pattern causes the anisotropy of the surface stress within the surface. The magnitude of the surface stress varies with increasing temperature, due to the competition between the thermal vibration induced charge redistribution and the thermal expansion effect. We further investigate the surface-dependent fracture behavior, showing that fracture strain is highly sensitive to surface termination, charge redistribution on the (100) and (010) surfaces enhances ductility, while asymmetric charge redistribution on the (001) surface weakens bonding and facilitates premature fracture. Overall, the presence of surfaces induces structural reconstruction, while the associated charge redistribution modifies the Coulombic interactions at the surface. These effects jointly alter the surface stress and ultimately influence the intrinsic mechanical behavior of CsPbI 3 . These findings will be valuable for future research on the charge-mechanics coupling at the surface of CsPbI 3 inorganic perovskite and the surface-related instability phenomena.