Synergistic effects of transmutation elements and molten salt corrosion on the evolution of core–shell structures and degradation mechanisms in SiC

First-principles calculations combined with ab initio molecular dynamics (AIMD) simulations were conducted to investigate the behavior of transmutation elements (Al, Be, Mg, Li) and the precipitate element Ni, together with corrosive species from molten salts (F, Cl, O, N, B, H) within 3C–SiC. The results indicate that: i) All non-metallic species spontaneously adsorb on the SiC surface, with adsorption energies ranging from −6.52 to −2.60 eV (P < N < O < B < Cl < F < H); O, N, and B form stronger bonds, whereas Cl, F, and H exhibit weaker interactions. Transmutation metals show pronounced surface segregation, with energies spanning −5.78 eV < Li < Mg < Be < Ni < Al < −1.64 eV, indicating a strong preference of Li and Mg for interfacial accumulation; ii) interstitial non-metal doping induces characteristic core–shell structures, manifested as elongated X–Si bonds and shortened C–Si bonds. Be doping enhances local bonding and structural stability, whereas Mg and Li incorporation reduces mechanical integrity; iii) AIMD simulations at 1023 K reveal that F atoms form stable bonds in the presence of transmutation elements, resist diffusion to vacancies, but can induce new vacancy formation, promoting the accumulation of corrosive species; iv) density of states analysis shows that F doping and vacancies introduce localized states or anomalous peaks near the Fermi level, substantially altering the electronic structure and acting as potential corrosion-active centers.