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First-principles calculations of LaNi_5-xSn_xH_y  intermetallics and intermediate phase

Dong CHEN , Jingdong CHEN , Yinglu ZHAO , Hailiang HUO , Benhai YU , Deheng SHI

金属学报(英文版) doi:10.1016/S1006-7191(08)60106-4

The crystal and electronic structures of LaNi_4.75Sn_0.25 intermetallics and LaNi_4.5Sn_0.5H_y (y=2.0, 2.5) intermediate phase have been investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Hydrogen occupation sites in LaNi_4.5Sn_0.5H_y have been determined based on Westlake$'$s criterions: (1) the minimum hole radius is 0.04~nm; (2) the minimum H-H distance is 0.21~nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n^*, 6m, 12o, 6m^* sites in LaNi_4.5Sn_0.5H_2.0 and the 6m^*, 4h, 6m, 12o, 12n^* sites in LaNi_4.5Sn_0.5H_2.5. The specific coordinates of hydrogen atoms in LaNi_4.5Sn_0.5H_y are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi₅. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi_4.5Sn_0.5-H system. Lattice expansion and increment of Fermi energy E _F show that both Sn and H atoms decrease structural stability of these alloys.

关键词: Rare-earth intermetallics , null , null , null