Hydrogen storage properties of ternary ordered cubic Laves phase Cu3Cd2In: Electronic structure and bonding approach

Ternary Cu3Cd2In represents an ordered variant of cubic MgCu2-type (AB(2)-type) Laves phase {space group P4(1)32 (213); lattice parameter a = 7.3254(2) angstrom}; where an unusual atomic ordering between the neighbouring Cd and In was observed. Basic hydrogen storage properties of Cu3Cd2In were investigated by first-principles density functional theory calculations. Along with three independent crystallographic positions, three types of interstitial sites(i): (i(Cu3In), i(Cu2CdIn), i(Cu2Cd2)) are present. H atom(s) can be accommodated in the interstitial sites. The Cu-rich i(Cu3In) site, with the highest binding energy, was found to be most preferable for H, followed by the other two sites. The hydrogen binding energy remains nearly in the same range up to 4 H/unit cell, with similar to 7.5% volume increment. Electronic structure and chemical bonding of hydrogenated configurations were analysed by density of states (DOS), crystal orbital Hamilton population (COHP) and Bader charge analysis with the aim to explore the host-guest interactions.