First-Principles Study of the Effects of Carbon, Nitrogen, and Oxygen on Helium Behavior in Body-Centered-Cubic Vanadium

Density functional theory calculations were used to study the effects of inherent impurities C, N, and O on the stability and the self-trapping of interstitial He atoms in body-centered-cubic vanadium (V). The most stable site for the He atom nearby C, N, and O is the tetrahedral interstitial site (T-site) rather than the octahedral interstitial site (O-site). The presence of C, N, or O impurities reduces the stability of He in the T-site according to the calculated formation energies. The addition of C and O atoms is beneficial for He self-trapping while the addition of the N atom prevents He self-trapping in vanadium. The stable configurations for X_n-vacancy₁ (X_nVa₁) are C₂Va₁, N₂Va₁, and O₂Va₁. The trapping energies of multiple He atoms captured by X_nVa₁ are investigated. Our results show that the presence of C, N, and O reduces vacancy trapping of He atoms. Our findings provide further understanding on the behavior of He atoms in vanadium with the influence of C, N, and O.