Ab initio tensile tests were applied to the non-polar interface of the {122} Σ = 9 tilt boundary in the cubic phase. The tensile strength and mechanical behaviour at zero temperature were examined by using a pseudopotential method which was based upon local density-functional theory. The interface was strong because of reconstruction of the interfacial bonds. The maximum tensile stress in uniaxial extension normal to the interface was about 42Gpa. This was equal to about 80% of the theoretical value. The Young's modulus and the fracture toughness were also comparable with the values for the bulk crystal. The back Si-C bond of the interfacial C-C bond broke first because the C-C bond had high strength and short length; like a diamond bond. The interfacial Si-C bonds then broke and, finally, the Si-Si bond. The Si-C bonds were rapidly stretched and broken if the bond-stretching exceeded about 20%, and the bond charge clearly disappeared when the bond-stretching exceeded about 30%.

Tensile Strength and Fracture of a Tilt Grain Boundary in Cubic SiC - a First-Principles Study M.Kohyama: Philosophical Magazine Letters, 1999, 79[9], 659-72