First principles study on the mechanical properties and generalized stacking fault energy of CsCl, CsBr and CsI

In this paper, the lattice constants, elastic anisotropies, and elastic constants (C11, C12 and C44) of three Cs halide materials, CsCl, CsBr and CsI have been investigated for the first time by using first-principles-based calculations, and the bulk modulus (B), shear modulus (G), and Young's modulus (E) of the materials have been obtained based on the calculated elastic constants, and the mechanical properties of the materials have been analysed. The elastic anisotropy of the material is calculated and the corresponding three-dimensional surface diagram is drawn. The generalized stacking fault energy (GSFE) curves of CsCl, CsBr and CsI were calculated and the generalized stacking fault energy (GSFE) surfaces were fitted. The calculations show that the elastic constant results for CsCl, CsBr and CsI are fully consistent with the Born stability criterion, i.e., all three materials are consistent with good mechanical stability. The 3D surface images representing the dependence of the elastic properties on the crystal orientation more intuitively reflect the degree of anisotropy of the materials in agreement with the information reflected by the anisotropy factor. By comparing the generalized stacking fault energy (GSFE) surfaces in the three directions of the materials, it is found that the slip of CsI intermetallic is the hardest and the generalized stacking fault energy (GSFE) on the {110} plane has the laws of CsI > CsCl > CsBr along the < 100>, < 110 > and < 111 > directions.