Atomic-scale simulations of ideal strength and deformation mechanism in β-SiC under H/He irradiation

Abstract We firstly investigated the mechanical responses of β-SiC to the tensile and shear strains under H/He irradiation using density functional theory, with a specific focus on the atomistic mechanism of deformation and fracture. The results revealed that the effect of introducing H/He on ideal strengths of tension and shear is limited, due to the strong sp 3 bonds of Si-C. However, somehow large disparity in failure was discovered after introducing H/He. Under the tension, all Si-C bonds along the tensile direction are synchronously broken, causing cubic-to-graphitic transformation in the perfect β-SiC, in contrast to the asynchronous breakage of Si-C bonds in the H/He-doping systems. Under the shear, H- and He-doping systems display individual cleavage-like modes of lattice instability, respectively, whereas structural transformation by re-bonding new Si-C bonds is responsible for the failure in the perfect β-SiC. The cleavage-like modes were discussed, combining a detailed analysis of electronic structure. The mechanical response to H/He irradiation distinguishes β-SiC from conventional metals presently applied in nuclear industry. The study may provide a clue for new design strategy of irradiation-tolerant materials for energy applications.