Ti掺杂对Li-Mg-N-H材料储氢性能影响的第一性原理研究

摘要/Abstract

摘要： 采用基于密度泛函理论的第一性原理赝势平面波方法,研究了Ti掺杂对Li₂MgN₂H₂材料储氢性能的影响及作用机理,计算给出了杂质替换能、生成焓、能带结构、态密度、差分电荷密度及布居等。研究表明,Ti掺杂Li₂MgN₂H₂体系时,其倾向于替换其中的Mg原子,且当替换8c位置的Mg时,杂质替换能最低,晶体结构最为稳定。生成焓计算结果表明,Ti掺杂能够有效降低Li₂MgN₂H₂的结构稳定性,有利于其吸氢反应的进行。进一步结合电子结构分析发现,Ti掺杂使得Li₂MgN₂H₂材料的晶胞体积增大,能隙降低,同时Ti与N原子之间较强的相互作用使得Li—N和N—H键的成键峰峰值降低,键强减弱,这些因素均有利于Li₂MgN₂H₂材料吸氢动力学性能的提高。

关键词: 第一性原理, Li-Mg-N-H, Ti掺杂, 生成焓, 电子结构, 储氢

Abstract: The effect of Ti doping on the hydrogen storage performance of Li₂MgN₂H₂ materials and its mechanism were investigated by the first-principles plane-wave pseudopotential method based on the density functional theory. The impurity replacement energy, formation enthalpy, energy band structure, density of states, differential charge density and population were calculated. The results show that when Ti atom is doped with Li₂MgN₂H₂ system, it tends to occupy the Mg lattice sites, and when replacing Mg at position 8c, the impurity replacement energy is the lowest and the crystal structure is the most stable. The calculation results of the formation enthalpy indicate that Ti doping can effectively reduce the structural stability of Li₂MgN₂H₂, which is beneficial to its hydrogen absorption reaction. Further combined with the analysis of the electronic structure, it is found that for the Li₂MgN₂H₂ materials after Ti doping, the unit cell volume increases and the energy gap reduces. At the same time, because of the strong interaction between Ti and N atoms, the peak value of the Li—N and N—H bonds reduces, and the bond strength weakens. These factors are all conducive to the improvement of the hydrogen absorption kinetic performance of the Li₂MgN₂H₂ material.

Key words: first-principle, Li-Mg-N-H, Ti doping, enthalpy of formation, electronic structure, hydrogen storage

中图分类号:

闫敏艳, 宫长伟, 张鹤, 张敏刚. Ti掺杂对Li-Mg-N-H材料储氢性能影响的第一性原理研究[J]. 人工晶体学报, 2022, 51(2): 297-303.

YAN Minyan, GONG Changwei, ZHANG He, ZHANG Mingang. First-Principles Study on the Effect of Ti Doping on Hydrogen Storage Performance of Li-Mg-N-H Materials[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2022, 51(2): 297-303.

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