影响及其微观机理
(1. 长沙理工大学 汽车与机械工程学院，长沙 410114；
2. 湖南大学 材料科学与工程学院，长沙410082；
3. 湖南大学 汽车车身先进设计制造国家重点实验室，长沙 410082)
摘 要: 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。
关键字: Mg2Ni；储氢合金；相结构稳定性；赝势平面波；电子结构
phase structural stability of Mg2Ni alloy
（1. Institute of Automobile and Mechanical Engineering,
Changsha University of Science and Technology, Changsha 410114, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China;
3. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China）
Abstract:The influence and micromechanism of Al or Ti doping on the phase structural stability of Mg2Ni hydrogen storage alloy were investigated by the first-principles pseudopotential plane-wave method. The results show that within the range of doping concentration x from 0 to 0.5, the phase structural stability of Mg2Ni-type Mg2−xMxNi(M=Al, Ti) solid solution alloys is improved with increasing Al concentration. By contrast, the stability is weakened with increasing Ti concentration. These solid solution alloys all exhibit thermal instability with respect to the cubic Mg3MNi2(M=Al, Ti) compounds. They are likely to decompose into the multi-phases as composed of cubic Mg3MNi2(M=Al, Ti) and hexagonal Mg2Ni, which are in good agreement with the experimental results. The analysis of electronic structures shows that the phase structural stability of Mg2Ni hydrogen storage alloy with Al or Ti doping is closely associated with the bonding electron number of the doping systems, which originate mainly from lower energy ranges below Fermi energy level.
Key words: Mg2Ni; hydrogen storage alloy; phase structural stability; pseudopotential plane-wave; electronic structure
