First-principles calculations of LaNi_(5-x)Sn_xH_y intermetallics and intermediate phase
来源期刊：Acta Metallurgica Sinica2009年第5期
论文作者：Deheng SHI Yinglu ZHAO Hailiang HUO Dong CHEN Benhai YU Jingdong CHEN
Key words：Rare-earth intermetallics; Hydrogen storage; Site occupancy; Electronic structure;
Abstract: The crystal and electronic structures of LaNi_(4.75)Sn_(0.25) intermetallics and LaNi_(4.5)Sn_(0.5)H_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_(4.5)Sn_(0.5)H_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_(4.5)Sn_(0.5)H_(2.0) and the 6m~*, 4h, 6m, 12o, 12n~* sites in LaNi_(4.5)Sn_(0.5)H_(2.5). The specific coordinates of hydrogen atoms in LaNi_(4.5)Sn_(0.5)H_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_(4.5)Sn_(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.
Deheng SHI1，Yinglu ZHAO2，Hailiang HUO1，Dong CHEN1，Benhai YU1，Jingdong CHEN1
(1.College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China;
2.College of Physics and Electronic Engineering, Ludong University, Yantai 264025, China)
Abstract:The crystal and electronic structures of LaNi_(4.75)Sn_(0.25) intermetallics and LaNi_(4.5)Sn_(0.5)H_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_(4.5)Sn_(0.5)H_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_(4.5)Sn_(0.5)H_(2.0) and the 6m~*, 4h, 6m, 12o, 12n~* sites in LaNi_(4.5)Sn_(0.5)H_(2.5). The specific coordinates of hydrogen atoms in LaNi_(4.5)Sn_(0.5)H_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_(4.5)Sn_(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.
Key words:Rare-earth intermetallics; Hydrogen storage; Site occupancy; Electronic structure;
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