H_2反应球磨Mg-Ge混合物体系解氢能力的密度泛函理论研究

A Density-functional Theory Study on Dehydrogenating Properties of Milling of the Mg-Ge Mixture Under Hydrogen

通过采用基于密度泛函理论的第一性原理赝势平面波方法,计算H2反应球磨Mg-Ge混合物体系氢化相的能量与电子结构,结果发现:不同含量Ge固溶于MgH2形成的(MgGe)H2固溶体,与未进行Ge合金化的MgH2体系相比,体系相结构稳定性变差;Ge在MgH2中固溶量达到一定程度时,发生2MgH2+GeMg2Ge+2H2化学反应,此时体系解氢能力虽与未合金化时相比有所增强,但不及Ge固溶MgH2体系时的情形;Ge合金化提高MgH2体系解氢能力的主要原因在于Ge与Mg原子之间的成键作用导致H与其近邻的Mg原子之间的成键作用减弱。

Energy and electronic structure of the hydride phase of milling of the Mg-Ge mixture under hydrogenwere calculated by using a first-principles plane-wave pseudopotential method. The results show that the structuralstability of the alloying system is reduced when a little Ge dissolve into magnesium hydride, with the raising of Ge con-tent, Mgz Ge compound may be formed by the reaction 2MgH2 q-Ge→←Mg2 Geq-2H2. At the same time dehydrogena-ting properties of the system is improved compared without Ge addition, but reduced than that of （MgGe）H2 solid so-lutions. After compared the densities of states （DOS） and the charge distribution of MgH2 with and without Ge allo-ying, it is found that the improvement of dehydrogenating properties of MgH2 dissolved by a little Ge attributes to theweakened bonding between magnesium and hydrogen caused by the interactions between Ge and hydrogen.