Hardness of cubic spinel Si3N4

Abstract

The hardness of cubic spinel Si3N4 was calculated by using our microscopic model of hardness combined with first principles calculation. The calculated Vickers hardness is only 33.3GPa in good agreement with its experimental values reported recently, indicating that the cubic spinel Si3N4 is not a superhard material. Our calculation results also implicate a more important fact that predicting the hardness of a material based on its bulk modulus or shear modulus is impertinent.