Driving mechanism of neutron-irradiation-induced amorphization in silicon carbide

In this study, irradiation-induced amorphization in silicon carbide (SiC) by 1 MeV neutrons was investigated using molecular dynamics (MD) simulations. The crystalline-to-amorphous (c-a) transition occurred at 0.27 dpa with a structure relaxation of the whole lattice. Fast neutrons have produced many displacement spikes with unsaturated coordinated atoms at the center. Our results have shown that the two-coordinated Si atoms play a key role in defect accumulation and amorphization. There are two types of such defects: displaced-atom-induced (D-type) defect and vacancy-induced (V-type) defect. The D-type defect tends to form clusters and promotes the formation of C Frenkel pairs after 0.13 dpa. The V-type defect enhances the driving force of c-a transition and finally triggers amorphization at high concentration based on thermodynamics. -- Research Highlights: → The mechanism of neutron-induced amorhpization in 3C-SiC is homogenous. → A sudden structure relaxation occurs at crystalline-to-amorphization transition point.→ Two coordinated Si atom clusters are formed at the center of displacement spikes. → This defect plays a key role in defect accumulation and amorphization.