掺杂元素对Mg_2NiH_4稳定性影响的第一性原理研究  

First-principles investigations of the influence of alloying elements on the stability of Mg_2NiH_4

作　　者：肖荣军[1] 郭进[2] 黄刚[1] 张秀彦[1] 朱基珍[1] 

机构地区：[1]广西工学院信息与计算科学系,柳州545006 [2]广西大学物理科学与工程技术学院,南宁530004

出　　处：《原子与分子物理学报》2009年第5期969-977,共9页Journal of Atomic and Molecular Physics

基　　金：广西工学院硕士科研基金(院科研0816206)

摘　　要：本文采用基于密度泛函理论(DFT)的第一原理赝势平面波(PW-PP)方法,计算了低温相Mg_2NiH_4和(Mg_2Ni,X)H4(X=Ag,Al,Ti或Zr)的生成热及电子结构,分析了掺杂元素对Mg2Ni氢化物稳定性的影响.结果表明,掺杂导致了合金氢化物生成热的绝对值降低,合金氢化物的稳定性下降,且发现掺杂元素电负性越大,氢化物越不稳定.从电子态密度图和Mulliken布居数分析知道,掺杂后合金氢化物释氢能力增强的主要原因在于Ni-H之间的成键减弱,以及掺杂元素诱导费米能级E_F处电子数浓度N(E_F)的增加.The heat of formation and electronic structures of LT-Mg2 NiH4 and （Mg2Ni, X）H4 （X= Ag, Al, Ti or Zr） were calculated by plane wave pseudopotential （PW-PP） method which is based on density functional theory, and the influences of alloying elements on the stability of Mg2 Ni hydride were investigated. A low absolute value of the negative heat of formation of （Mg2Ni,X）H4 （X=Ag, Al, Ti or Zr） compared with that of Mg2NiH4 indicates that the alloying atoms X（X=Ag, Al, Ti or Zr） befit to improve the dehydrogenating properties of Mg2NiH4. An interesting trend is found that, the more electronegative of alloying elements, the more unstability of hydride systems. According to the densities of states and Mulliken population analysis, it was found that the improvement of the dehydrogenating properties of Mg2NiH4 originates from the increasing of the densities of electron numbers N（EF） at Fermi level （EF） and the weal：el bonding between Ni and H of （Mg2Ni,X）H4 （X=Ag, Al, Ti or Zr） which is caused by the addition of Ag, Al, Ti or Zr atoms. Hence, the dehydrogenating properties of Mg2NiH4 are expected to be improved to a different extent by the addition of alloy elements.

关 键 词：稳定性 电子结构 MG2NIH4 

分 类 号：TG139.7[一般工业技术—材料科学与工程]