Mechanical anisotropy and origin of shear plastic deformation of tetragonal B4C4

Abstract

Based on first-principle calculations, we fundamentally investigate the anisotropic mechanical properties and atomistic deformation mechanism of the recent proposed ultra-incompressible tetragonal t-B4C4. The obtained results reveal that the t-B4C4 exhibits a pronounced elastic anisotropy according to the distributions of elastic moduli along the principal crystal orientations. It is found that the ideal shear strength in the direction of dominates the shear plastic deformation for t-B4C4. The lattice instability of the t-B4C4 can be revealed by the bond lengths and electron localization function as functions of shear strain. The results show that the failure modes of t-B4C4 can be attributed to the breaking of C-B bonds in the C2B8 double quadrangular pyramid.