First-principles study of hydrogen behavior in V-Cr-Ti alloys

V-Cr-Ti alloys are considered as one of the most promising candidate structural materials for fusion reactor. Hydrogen impurities originated from bombarding with reaction plasma as well as various nuclear transmutation reactions have a considerable influence on the performance and stability of V-Cr-Ti alloys. To understand the microscopic mechanism, we have simulated the behaviors of H atoms inside the pure vanadium solid as well as V-based alloys (V-4Cr-4Ti and V-5Cr-5Ti) using first-principles approach. The binding energies or absorption energies for H atom inside different interstitial sites were compared to determine the optimal trapping sites. Interaction between two interstitial H atoms was calculated and fit into a screened Coulomb potential. H atom prefers to diffuse along path between two nearest interstitial sites with low energy barriers of 0.20-0.34 eV.