Nonlinear Mechanical Properties of Polymorphic CsPbI3 Perovskite from Reactive Molecular Dynamics Simulations

All-inorganic cesium lead triiodide (CsPbI3) perovskitemakes efficient solar cells, for which the nonlinear induced fractureproperties are important for its mechanical stability, but these nonlinearmechanical behaviors under finite deformation remain unclear. Here,we perform reactive molecular dynamics simulations to investigatethe mechanical properties of CsPbI3 of different phasesunder finite deformation. Our simulations reveal that Young'smodulus and Poisson's ratio exhibit anisotropy in the linearelastic region. The orthorhombic phase exhibits a lower hardness andhigher flexibility compared to the tetragonal and cubic phases, resultingin higher susceptibility to stress. The average atomic charge decreaseswith increasing strain and concentrates at the cracks during fractureprogress. We also discover that negative Poisson's ratio occursin the xz-direction during finite deformation oftetragonal and orthorhombic phases, which is well explained by thePb-I-Pb angle perpendicular to the xy-plane. Our findings provide valuable insights into the mechanicalbehavior and fracture characteristics of CsPbI3 perovskite,which have important implications for designing perovskite-based devicesfor different applications.

Automated summary

In this study, the mechanical properties of different phases of CsPbI3 under finite deformation were investigated using reactive molecular dynamics simulations. Anisotropy in Young's modulus and Poisson's ratio was observed in the linear elastic region. The orthorhombic phase showed lower hardness and higher flexibility compared to the tetragonal and cubic phases, leading to higher susceptibility to stress. The average atomic charge decreased with increasing strain and concentrated at cracks during fracture progression. Additionally, negative Poisson's ratio was found in the xz-direction during finite deformation of the tetragonal and orthorhombic phases, which could be explained by the Pb-I-Pb angle perpendicular to the xy-plane. These findings provide valuable insights into the mechanical behavior and fracture characteristics of CsPbI3 perovskite, with implications for designing perovskite-based devices for various applications.