Theoretical study of YFe2Hx (x = 0-5): A comparison between cubic and orthorhombic phases

The stability of binary intermetallic Laves phase YFe2 and its hydride YFe2Hx (x = 0-5) are studied using first-principles calculation. Accompanied with the analysis of the hydrogen binding energy and the formation enthalpy in various interstitial sites in YFe2Hx, a transition of the stability from cubic to orthorhombic phase is found when hydrogen concentration increases to 1.5H/f.u. It is found that the hydrogen binding energy is very sensitive to the magnetic property of neighboring atoms. To get a further insight of the transition, we take into account external strains, as well as chemical substitution at Y site. It turns out that the transition point can be tuned by strain and chemical bonding.