中文摘要：

采用基于密度泛函理论的第一性原理方法研究了稀土和过渡元素替代对MgH_2储氢体系的加氢反应影响机理。研究发现氢原子可以在Mg表面形成稳定的吸附。稀土和过渡元素Fe,V,Ti,Nb,La替代Mg降低了H的吸附能,表明合金元素可以提高H在Mg表面吸附的稳定性。表面吸附体系稳定性由高到低的次序为：Nb,Fe,V,Ti,La掺杂Mg表面。电子结构及电荷布局分析结果表明,稀土La与H间电子耦合较弱;而过渡金属原子明显与H有较强的共价相互作用。H能稳定的吸附在Mg的表面,为H进一步向Mg体内扩散提供了条件,从而为Mg氢化生成MgH_2提供了H源。此外,吸附H也可能会与掺杂元素生成氢化物（如TiH2）,这些氢化物也是Mg氢化生成MgH_2的催化剂。合金原子与H间存在的强的共价作用是提高MgH_2的加氢性能的决定原因。

英文摘要：

The pseudopotential plane-wave method based on density functional theory was used to study the influences mechanisms of the transition metal elements and rare earth substitution on the hydrogenation of MgH_2.The results show that H atom can be adsorbed on the Mg（0001）surface stably.The substitution of rare earth and transition elements Fe,V,Ti,Nb,La for Mg in the Mg surface decreases the adsorption energies of H,which shows that the alloying element can improve the stability of H adsorption on Mg surface.The ranking of the stability of the surface adsorption system from high to low is：Nb,Fe,V,Ti,La doped Mg surface.The analysis results of electronic structure and charge population show that the electron coupling between La and H is weak;while the covalent interaction between transition metal atom and H is obviously stronger.The stable adsorption of H on the surface of Mg provides the condition for H to further diffuse into the bulk Mg,and provides a H source for Mg hydrogenation to produce MgH_2.In addition,adsorption of H may also be related to the formation of hydrides（such as TiH2）.Such hydrides are also the catalysts in Mg hydrogenation to produce MgH_2.A strong covalent interaction between alloy atoms and H is a crucial factor to improve hydrogenation performance of MgH_2.