MgH2-X(X=Si,Ge,Sn,Pb)体系解氢能力的第一原理计算

采用基于密度泛函理论的第一原理赝势平面波方法,研究了MgH2-X(X=Si,Ge,Sn,Pb)合金化体系的能量、几何与电子结构.负形成热的计算发现:合金化元素X在镁氢化合物(MgH2)中少量固溶时,体系相结构稳定性变差,预示着解氢能力得到改善.电子态密度(DOS)与电子密度的进一步分析发现:镁氢化合物X合金化后,X与其周围的H原子相互作用不明显,而Mg-H之间的成键作用减弱.体系Ge合金化解氢能力增强的理论计算与实验结果一致,预测Si,Sn,Pb少量固溶于MgH2能提高体系的解氢能力.

First-Principles Calculation of Dehydrogenating Properties of MgH2-X(X=Si, Ge, Sn, Pb) Systems

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energy and electronic structure of magnesium hydride(MgH_2) alloyed by X(X=Si,Ge,Sn,Pb).Through calculations of the negative heat of formation of magnesium hydride alloyed by X,it was found that when a little X dissolve into magnesium hydride,the structural stability of alloying systems decreases,which indicates that the dehydrogenation properties of MgH_2 can be improved.After comparing the densities of states(DOS) and the charge distribution of MgH_2 with and without X alloying,it was found that the improvement of the dehydrogenation properties of MgH_2 alloyed by X attributes to the fact that the weakened bonding between magnesium and hydrogen is caused by no stronger interactions between X and hydrogen.The calculation results of the improvement of the dehydrogenation properties of MgH_2-X(X=Ge) systems are in agreement with the experimental results.Hence,the dehydrogenation properties of MgH_2 are expected to be improved by the addition of Si,Sn,Pb alloying elements.