(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贗勢平面波方法， 計算了不同含量的Ti固溶于鎂氫化合物(MgH2)中形成(MgTi)H2， 析出TiH2相形成TiH2/ MgH2相界的能量與電子結(jié)構(gòu)。 負(fù)合金形成熱的計算結(jié)果表明： 對MgH2進(jìn)行Ti合金化， 體系相結(jié)構(gòu)的穩(wěn)定性變差， Ti在MgH2中固溶以及TiH2/ MgH2相界的存在均有利于MgH2解氫能力的增強(qiáng)。 電子態(tài)密度(DOS)與電子密度的進(jìn)一步分析發(fā)現(xiàn)： 合金化體系解氫能力增強(qiáng)的主要原因在于Mg—H之間的成鍵作用較弱， 以及Ti誘導(dǎo)費(fèi)米能級EF處電子密度N(EF)的增加和EF附近HOMO-LUMO能隙ΔEH-L的變窄甚至消失。
關(guān)鍵字: MgH2; 贗勢平面波； 解氫能力； 電子結(jié)構(gòu)
（School of Materials Science and Engineering, Hunan University,
Changsha 410082, China）
Abstract: Using a first-principles plane-wave pseudopotential method, the energetics and electronic structure of (MgTi)H2 formed by titanium dissolving into magnesium hydride and TiH2/MgH2 interface model were investigated. The heats of formation of considered systems were estimated from the electronic structure calculations, a reduction of the absolute value of the negative heat of formation of titanium alloying systems was found as compared with that of MgH2. This indicates that titanium alloying befits the improvement of the dehydrogenating properties of MgH2. After compared the densities of states (DOS) and the charge distribution of MgH2 with and without titanium addition, it is found that the improvement of dehydrogenating properties of MgH2 caused by titanium alloying originates from the weakened bonding between magnesium and hydrogen, and the increasing of the valence electrons at Fermi level and decreasing of the HOMO-LUMO gap (ΔEH-L) near Fermi level.
Key words: MgH2; plane-wave pseudopotential theory; dehydrogenating properties; electronic structure
