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

CX Cui and JW Jiang, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 11760-11766 (2023).

DOI: 10.1021/acs.jpcc.3c02939

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.

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