Structural stability and magnetic properties of WFeH phases

• H at T site of W50Fe50 is energetically unstable and will relax to O site.
• WH bond is generally stronger with lower bond energy than FeH bond.
• Zero-point energy of H has negligible effect on structural stability of WFeH.
• Addition of W and H could reduce magnetic moments of W50Fe50 and Fe.
• Calculated results are in good agreements with experimental observations.

First principles calculation reveals that hydrogen at the tetrahedral site of B2 W50Fe50 is energetically unstable and will relax to the octahedral site, which is quite different from the stable tetrahedral site of BCC W and Fe. It is also shown that the WH bond is generally stronger with lower bond energy than the FeH bond, and that zero-point energy of hydrogen has a negligible effect on structural stability of WH, FeH, and W50Fe50H phases. Moreover, both W and H atoms have important effects to reduce magnetic moments of W50Fe50 and Fe, while their intrinsic mechanisms are quite different, i.e., the addition of W induces the decrease of the bond number of FeFe, and the addition of H brings about the decrease of FeFe bond length. The calculated results are in good agreements with experimental observations in the literature, and are discussed in terms of electronic structures and bond characteristics.