(1. 湖南大学 汽车车身先进设计制造国家重点实验室，长沙 410082；
2. 湖南大学 材料科学与工程学院，长沙 410082)
摘 要: 采用基于密度泛函理论的第一原理计算方法，对高、低温Mg2NiH4氢化物的晶体与电子结构及稳定性能进行研究。合金形成热及氢原子解离能的计算结果表明：相对低温相而言，高温Mg2NiH4相具有较低的相结构稳定性及较高的解氢性能。电子结构分析发现：两种氢化物相结构稳定性存在差异的主要原因在于费米能级EF处的价电子数N(EF)的多少及EF附近HOMO-LUMO能隙∆EH-L的大小不同，而两者解氢性能存在差异则归因于Ni—H及Mg—NiH4间相互作用的强弱不同；此外，在两种氢化物的NiH4单元内，Ni—H间均存在复杂的离子—共价键的相互作用。
关键字: Mg2NiH4；密度泛函理论；形成热；电子结构
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:A first-principles calculation method based on density functional theory was used to investigate the crystal and electronic structures as well as stability properties of high and low temperature Mg2NiH4 hydrides. The calculation results of the formation heat and dissociation energy of H atoms show that high temperature Mg2NiH4 has a low structural stability and an enhanced dehydrogenation property, compared with low temperature phase. Further analysis of the electronic structures shows that the difference in the stability between high and low temperature Mg2NiH4 mainly originates from the differences in the valence electrons at Fermi level (EF) and the HOMO-LUMO gap (∆EH-L) around EF, whereas the enhanced dehydrogenation property of high temperature Mg2NiH4 relative to low temperature phase is attributable to the weakened interactions of Ni—H and Mg—NiH4. Besides, there exist complex ionic-covalent interactions between Ni and H within NiH4 units in both of the hydrides.
Key words: Mg2NiH4; density functional theory; formation heat; electronic structure
