(1. 湖南大學(xué) 汽車車身先進設(shè)計制造國家重點實驗室，長沙 410082；
2. 湖南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410082)
摘 要: 采用基于密度泛函理論的第一原理計算方法，對高、低溫Mg2NiH4氫化物的晶體與電子結(jié)構(gòu)及穩(wěn)定性能進行研究。合金形成熱及氫原子解離能的計算結(jié)果表明：相對低溫相而言，高溫Mg2NiH4相具有較低的相結(jié)構(gòu)穩(wěn)定性及較高的解氫性能。電子結(jié)構(gòu)分析發(fā)現(xiàn)：兩種氫化物相結(jié)構(gòu)穩(wěn)定性存在差異的主要原因在于費米能級EF處的價電子數(shù)N(EF)的多少及EF附近HOMO-LUMO能隙∆EH-L的大小不同，而兩者解氫性能存在差異則歸因于Ni—H及Mg—NiH4間相互作用的強弱不同；此外，在兩種氫化物的NiH4單元內(nèi)，Ni—H間均存在復(fù)雜的離子—共價鍵的相互作用。
關(guān)鍵字: Mg2NiH4；密度泛函理論；形成熱；電子結(jié)構(gòu)
（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
