An ab initio study of the ideal tensile and shear strength of single-crystal β–Si₃N₄

In this study, the ideal tensile and shear strength of single-crystal β–Si₃N₄ was calculated using an ab initio density functional technique. The stress-strain curve of the silicon nitride polymorph was calculated from simulations of uniaxial strain deformation. In particular, the ideal strength calculated for an applied ∈₁₁ tensile strain was estimated to be approximately 57 GPa. Recently, a good correlation was reported between the shear modulus of high-strength materials and the experimentally determined Vickers indentation hardness value. Using the reported correlation an estimate was made of the Vickers indentation hardness of single-crystal β–Si₃N₄: approximately 20.4 GPa.