Thermodynamic modeling of hydrogenation of C14 TiMnx alloys

Abstract

C14 TiMnx-type alloys are promising hydrogen storage materials. However, their thermodynamic properties during hydrogenation cannot be easily predicted since their thermodynamics has not been modeled. Here, we present a CALPHAD-type thermodynamic description of the C14 TiMn2-H system. A sublattice model, [Mn, Ti]2[Mn,Ti]1[H,Va]3, was adopted for the C14 phase according to a first-principles calculation, and thermodynamic parameters were assessed using experimental pressure-composition-temperature data. The assessed thermodynamic parameter set reproduces the experimental pressure-composition-temperature data of C14 phases across different compositions. The present work provides a basis for thermodynamic modeling of hydrogenation in multicomponent C14 alloys and will contribute to the efficient design of hydrogen storage materials based on C14 alloys.