Theoretical investigations for MFe2 (M = Y, La) Laves alloy and hydrides HxMFe2: Structural stability, lattice thermodynamics, and elastic properties

Abstract Based on the first-principles calculations, the stable structures of FexM1-x (M = Y, La) binary alloy have been determined according to the formation enthalpy, and the calculated binding energy of hydrides as a function of chemical potential show that the YFe2H4.5 is stable. The thermodynamic stabilities of target alloys and hydrides at various temperatures have further been confirmed using the quasi harmonic approximation in lattice vibration theory. The nudged elastic band method (NEB) is used to investigate the diffusion of hydrogen atoms at different interstitials. The charge density distribution of YFe2 and YFe2H5 has been analyzed to demonstrate the structural stability and the dehydrogenation process. The elastic modulus of YFe2, YFe2H5, LaFe2 and LaFe2H5 will decrease as the temperature increases, with a weaker anisotropy in the Y–Fe system than that in the La–Fe system.