中文摘要：

用基于密度泛函理论的第一性原理赝势平面波方法,计算了Cr合金化前后Mg2Ni相及其氢化物的能量与电子结构。合金形成热的计算结果表明：Cr合金化Mg2Ni,形成Mg（I）CrNi的相结构最稳定,其中,Cr原子最易占据Mg（I）：（0.5,0,z）,z=l/9位置;进一步对其氢化物的解氢反应热进行计算,发现Cr合金化Mg2Ni氢化物后,体系解氢所需吸收的热量与合金化前相比明显降低,体系的解氢能力得到增强;电子态密度（DOS）、密集数与差分电荷密度的计算结果发现：Mg（I）CrNi相结构最稳定的主要原因在于体系在费米能级（EF）处附近的成键电子数最多;而Cr合金化Mg2Ni氢化物体系解氢能力增强的主要原因在于：Cr合金化后导致体系的稳定性降低,削弱了H-Ni和H-Mg间的成键作用。

英文摘要：

By first-principles plane-wave pseudopotential method based on the density functional theory,the energetics and electronic structures of Cr alloying Mg2Ni phase and corresponding hydrides were investigated.The results of heat of formation show that Cr atoms are most likely to occupy Mg（I）：（0.5,0,z）,z=l/9,and the Mg（I）CrNi 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 compared with pure Mg2Ni hydride,an obvious reduction of the absolute value of reaction heat of dehydrogenating of Cr alloying systems indicates that Cr alloying can benefit the improvement of the dehydrogenating properties of Mg2Ni hydride.Compared the density of states（DOS）,charge population and the electronic charge density difference of Mg2Ni hydride with and without Cr alloying,it is found that the Mg（I）CrNi phase which has the highest structure stability can attribute to the most valence electron numbers near Fermi level in this structure compared with the other structures.It is also found that the improvement of dehydrogenating properties of Cr alloying Mg2Ni hydride mainly originates from the lower structure stability of system and the weakened interactions between hydrogen and nickel,hydrogen and magnesium.