A comparative AIMD study of electronic excitation-induced amorphization in 3C-SiC, TiC, and ZrC

In the present study, an ab initio molecular dynamics (AIMD) method was employed to investigate the effect of electronic excitation on the micro-structural evolution of 3C-SiC, TiC, and ZrC. The AIMD results demonstrated that electron excitation induces a crystalline-to-amorphous phase transition in all carbide compounds. The determined threshold electronic excitation concentration for 3C-SiC, TiC, and ZrC at 300 K is 4.06%, 5.28%, and 4.26%, respectively. The mean square displacement of C atoms is larger than those of Si, Zr, and Ti atoms, which results from the smaller atomic mass of the C atom. These results indicate that the structural amorphization of 3C-SiC, TiC, and ZrC is primarily attributed to the displacement of C atoms. It is noted that amorphization induced by electronic excitation represents a solid–solid transition rather than a solid–liquid transition. It is further verified that the ⟨Si−C⟩ bond is a covalent characteristic, whereas the ⟨Ti−C⟩ or ⟨Zr−C⟩ bond is a mixture of ionic, metallic, and covalent characteristics, which may lead to different radiation tolerances of carbide compounds. The present results suggest that electronic excitation may contribute to the structural amorphization of carbides under low- or medium-energy electron and ion irradiation, and advance the fundamental comprehension of the radiation resistances of carbide compounds.