Structural stability and magnetic properties of WFeH phases

摘要

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 W-H bond is generally stronger with lower bond energy than the Fe-H 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 Fe-Fe, and the addition of H brings about the decrease of Fe-Fe 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. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.