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采用第一性原理赝势平面波方法,研究元素Al和Ti掺杂对Mg2Ni储氢合金相结构稳定性的影响及其微观机理。结果显示:在掺杂浓度x=0～0.5范围内,所形成的Mg2Ni型Mg2-xMxNi(M=Al,Ti)固溶体合金的相结构稳定性随Al掺杂浓度的增大而增强,随Ti掺杂浓度的增大而减弱,且Mg2-xMxNi(M=Al,Ti)固溶体合金相对于立方结构的Mg3MNi2(M=Al,Ti)化合物呈现热力学不稳定性,极易分解成由立方结构Mg3MNi2(M=Al,Ti)和六方结构Mg2Ni组成的复合相,计算结果与实验结果吻合。电子结构分析表明,Al、Ti掺杂Mg2Ni储氢合金的相结构稳定性与体系在低能级区的成键电子数密切相关。
First-principles pseudopotential plane-wave method was used to study the influence of element Al and Ti doping on the phase stability of Mg2Ni hydrogen storage alloy and its microscopic mechanism. The results show that the phase structure stability of Mg2Ni-type Mg2-xMxNi (M = Al, Ti) solid solution alloy increases with the increase of Al doping concentration in the range of doping concentration x = 0-0.5. (M = Al, Ti) solid solution alloy with respect to the cubic structure of Mg3MNi2 (M = Al, Ti) compounds showed thermodynamic instability, easily decomposed into cubic structure Mg3MNi2 (M = Al, Ti) and hexagonal Mg2Ni composite phase, the calculated results agree well with the experimental results. The electronic structure analysis shows that the phase structure stability of Al, Ti-doped Mg2Ni hydrogen storage alloys is closely related to the number of bonding electrons in the low-energy region.