Al 掺杂对Mg2Ni 合金的电子结构及贮氢性能的影响

采用基于密度泛函理论(DFT)的平面波赝势(PW-PP)方法, 计算Mg_2-xAl_xNiH₄ (x=0, 0.125, 0.25)合金的晶胞体积、电子态密度、键序、电荷布居、生成焓, 分析原子间成键和结构的稳定性, 研究Al 部分替代Mg 对Mg₂Ni 合金及其氢化物的结构和储氢性能的影响. 结果表明: 随着Al 含量的增加, Mg₂Ni 合金晶胞体积减小, 不利于氢原子进入合金中, 导致合金的储氢容量降低. 在Mg_2-xAl_xNiH₄ (x=0, 0.125, 0.25)中, Mg-H和Al-H相互作用远小于Ni-H的相互作用, 随着Al 含量的增加, 氢化物生成焓减少以及Ni-H的相互作用减弱, 氢化物的结构稳定性降低, Al 部分替代Mg能有效改善Mg₂Ni 合金释氢动力学性能.

Effect of Doping with Aluminium on the Electronic Structure and Hydrogen Storage Properties of Mg2Ni Alloy

Using plane wave pseudopotential methods based on density functional theory,the unit cell volumes,the electronic densities of states,the bond orders,the charge populations,and the formation enthalpies of Mg2-xAlxNiH4(x=0,0.125,0.25) alloys were calculated.By analyzing atom bonding and structural stability,the effects of partially substituting Al for Mg on the structure and hydrogen storage property of the alloys and their hydrides were investigated.It was shown that the unit cell volume of the Mg2Ni alloy decreases with the increase of Al content;the decreased unit cell volume hinders the incorporation of hydrogen atoms,thus reducing the hydrogen storage capacity.For Mg2-x Al x NiH 4(x=0,0.125,0.25) hydrides,the Mg-H and Al-H interactions are much weaker than the Ni-H interaction.However,the Ni-H interaction is weakened and the hydride enthalpy of formation decreases with increased Al content.Although the stability of the hydride structure is weakened,hydrogen desorption kinetics for the Mg2 Ni hydride can be improved with the partial substitution of Al for Mg.