Electronic structure and site occupation for the intermediate phase of LaNi4.5Al0.5Hy

The crystal structure, electronic structure and hydrogen site occupancy of LaNi4.5Al0.5Hy intermediate phase (y=2.0y=2.0, 3.0, 4.0) have been investigated using the full-potential linearized augmented plane wave (FLAPW) method. For the first time we analyzed the interstitial site occupation of hydrogen atoms. The H atoms were found to prefer the 6m, 3f and 12n sites, while no 4h sites were occupied. A narrowed Ni-d band is found due to the lattice expansion: the total DOS at EFEF increases with yy, which indicates that the compounds become less stable. The interaction between Al and Ni, with H plays a dominant role in the stability of LaNi4.5Al0.5Hy intermediate phase. The smaller the shift of EFEF towards the higher energy region, the more stable the compounds will be. Our results are compared with experimental data and discussed in the light of previous works.