Structure and thermodynamic studies of the LaMgNi4 compound and its hydrides by density functional theory

Abstract Mg containing intermetallic compounds are promising candidates for hydrogen storage. However, the thermodynamic data required to assess the hydriding/dehydriding enthalpies of these compounds are not available yet. In the present work, first principles density functional theory calculations were used to predict the crystal structure, stability, and reaction enthalpies of a LaMgNi 4 compound. The cohesive energy ( E coh ) and enthalpies of formation (Δ H ) of the corresponding hydrides were calculated. It was found that the structural stability order was γ-LaMgNi 4 H 7 hydride > α-LaMgNi 4 H hydride > β-LaMgNi 4 H 4 hydride. The reaction enthalpies (Δ H R ) for dehydrogenation of the γ-LaMgNi 4 H 7 hydride, α-LaMgNi 4 H hydride, and β-LaMgNi 4 H 4 hydride were 32.67, 33.08, and 32.05 kJ/mol H 2 , respectively. The results proved theoretically that LaMgNi 4 hydrides had a low dissociation temperature. The electronic structures of the LaMgNi 4 compound and its hydrides were also calculated and the results indicated that LaMgNi 4 hydrides were promising candidates for reversible hydrogen storage.