First-principles calculations of hydrogen in perfect WFe and WFeNb crystals

First principles calculations reveal that the addition Nb in WFeH phases changes the preferred site, i.e., WFeH(O2) → WFeNbH(T), and the addition of Nb can decrease the structural stability of WFeNbH(T) phase. It is also shown that Nb-H bond should have a stronger chemical bonding than W-H bond and Fe-H bond in WFeNbH phases when the bond length is bigger than 1.8 Å, which account for favorable mechanical properties of WFeNbH phases. Additionally, the most probable paths of H diffusion in WFe and WFeNb phases are calculated. The values of barriers denote that the addition of Nb in WFeH phases can result in H diffusing rapidly. The calculated results are in good agreements with experimental observations in the literature, and are discussed in terms of electronic structures and bond characteristics.