Cu合金化Mg_2Ni氢化物能量与电子结构的赝势平面波计算  

Energetics and Electronic Structures of Cu Alloying Mg_2Ni Hydride from Plane-Wave Pseudopotential Method Calculation

作　　者：张健[1] 周惦武[1] 彭平[1] 刘金水[1] 

机构地区：[1]湖南大学汽车车身先进设计制造国家重点实验室,湖南长沙410082

出　　处：《稀有金属材料与工程》2008年第8期1336-1341,共6页Rare Metal Materials and Engineering

基　　金：教育部博士点基金(20020530012);国家重点基础研究发展规划(2006CB605104)

摘　　要：采用基于密度泛函理论的第一原理赝势平面波方法,计算了Cu合金化前后Mg2Ni相及其氢化物的能量与电子结构。负合金形成热的计算结果表明:Cu合金化Mg2Ni形成Mg2Ni(Ⅱ)''1-xCux(x=1/3)的相结构稳定性最高,两个Cu原子最易占据Ni(Ⅱ)的(0,0.5,0.16667)与(0.5,0,0.5)位置;进一步对其氢化物的解氢反应热进行计算,发现Cu合金化后,氢化物体系解氢反应热与合金化前相比,明显降低,表明Cu合金化Mg2Ni氢化物的解氢能力增强;电子态密度(DOS)与电子密度的计算结果发现:Mg2Ni(Ⅱ)''1-xCux(x=1/3)相结构最稳定的主要原因在于:Cu合金化后氢化物在费米能级处的成键电子数N(EF)与其它结构相比最少;而Cu合金化Mg2Ni氢化物解氢能力增强的主要原因在于:Cu合金化削弱了氢化物中Mg-Ni和Ni-H间的成键作用以及相应原子在低能级区成键电子数的减少。Using the first-principles plane-wave pseudopotential method, the energetics and electronic structures of Cu alloying Mg2Ni phase and corresponding hydrides were investigated. The results of negative formation heat show that two Cu atoms are most likely to occupy the two Ni（Ⅱ） atom sites at （0,0.5,0.166 67）and （0.5,0,0.5） in Mg2Ni crystal cell, and the Mg2Ni（Ⅱ）″ 1-xCux（x=1/3） phase has the highest structure stability; The reaction heat of dehydrogenating of the hydride systems is further estimated from the electronic structures calculation, it is found that as compared with pure Mg2Ni hydride, an obvious reduction of the absolute value of reaction heat of dehydrogenating of Cu alloying systems indicates that Cu alloying benefits the improvement of the dehydrogenating properties of Mg2Ni hydride. After compared the density of states（DOS） and the charge distributions of Mg2Ni hydride with and without Cu alloying, it is found that the Mg2Ni（ Ⅱ）″ 1-xCux（x=1/3）phase which has the highest structure stability attributes to the least valence electron numbers at Fermi level in this structure compared with the other structures; It is also found that the improvement of dehydrogenating properties of Cu alloying Mg2Ni hydride mainly originates from the weakened interactions between magnesium and nickel, nickel and hydrogen, and the reduction in the bonding electron numbers of the relevant atoms at lower energy level below Fermi level.

关 键 词：Mg2Ni相 MG2NIH4 赝势平面波方法 解氢反应热 解氢能力 电子结构 

分 类 号：TG146.11[一般工业技术—材料科学与工程]