Iodine Atom Diffusion in SiC and Zirconium with First-Principles Calculations

Iodine atom interstitial configurations and diffusion in bulk β-SiC and α-Zr are calculated using first-principles calculations and the nudged elastic band method. The formation energy of an I interstitial in bulk silicon carbide (SiC) is ten times higher than that of an I interstitial in bulk Zr. The I interstitial is very difficult to introduce into bulk SiC compared with the doping process in bulk Zr. The diffusion mechanisms of an I atom in SiC and Zr are exchange mechanisms. Iodine interstitial diffusion in bulk SiC is roughly an isotropic process along a path that is a series of combinations of I_Si → I_c and I_c → I_Si, with a diffusion barrier of 1.20 eV and an attempt-to-diffuse frequency Γ₀  25.12 THz. Meanwhile, I interstitial diffusion in bulk Zr is an anisotropic process. An I interstitial atom diffuses mainly between two Zr atom [0001] layers along a zigzag path with a diffusion barrier of 0.16 eV and an attempt-to-diffuse frequency Γ₀ = 2.88 THz. In general, the diffusion rate of an I interstitial in bulk SiC is lower than that in bulk Zr in the temperature range from 290 to 3000 K. The defect effect on I diffusion is an interesting topic for future study.