Density functional theory study on LaNi_4.5Al_0.5 hydride phase: electronic properties and sites occupation

In this paper the crystal structure, electronic structure and hydrogen site occupation of LaNi_4.5Al_0.5H_y hydride phase (y = 5.0, 6.0) have been investigated by using full-potential linearized augmented plane wave method. The hydrogen atoms were found to prefer the 6m, 12o and 12n sites, while no 4h sites were occupied. A narrowed Ni-d band is found due to the lattice expansion, the total density of states at E_F increases with y, which indicates that the compounds become less stable. The interaction between Al and Ni, H plays a dominant role in the stability of LaNi_4.5Al_0.5H_y hydride phase. The smaller the shift of E_F towards the higher energy region, the more stable the compounds will be. The obtained results are compared with experimental data and discussed in the light of previous works.