First-Principles Calculations of the Tensile Strength and Fracture of a Grain Boundary in SiC

Abstract

The tensile strength and fracture of the non-polar interface of the {122}Σ=9 coincidence boundary in cubic SiC have been examined by using the techniques of the first-principles molecular-dynamics method based on the density-functional theory. This interface is very strong because of the reconstruction of interfacial bonds. The tensile strength is about 80 % of that of bulk crystal. The Young's modulus and the fracture toughness are also comparable to the bulk values. The back Si-C bond of the interfacial C-C bond is broken first because of the large strength of the C-C bond. Critical bond stretchings for the Si-C bond breaking are observed. Changes in the electronic structure are analysed.