First-principles study of hydrogen capture, solution and mechanical effects in transition metal tungsten alloy W-TM (V, Nb, Ta)

Tungsten alloy as a candidate for plasma facing materials (PFMs) in thermonuclear fusion experimental reactor (Tokamak) is of great significance for the successful use of nuclear fusion. Therefore, it is worth exploring to understand the problems of solution and retention of hydrogen (H) and its isotopes in transition metal (TM) and tungsten (W) forming isotype alloys. Based on density functional theory, the effects of hydrogen solution in W-TM (TM=V, Nb, Ta) alloy on energetics, bond length, electronic structure and mechanical properties are studied by first-principles calculations. The calculated solution energy indicates that a single H atom is more easily trapped by tetrahedral interstitial sites in the W-TM alloy, and WV alloy has the strongest trapping ability for single H atoms and the strongest interaction between them. With the increase of H impurity atoms, H is more likely to form aggregation in W-TM. The accumulation of multiple hydrogen impurities will cause serious fluctuations in the mechanical properties and melting point of W-TM alloy, among which WV alloy is least affected by H accumulation and has a strong ability to resist the effect of H accumulation. The results can provide a reference for understanding the behavior of H in the plasma facing material.