Ce-Mg合金体系弹性性质与电子结构的第一性原理研究

为了探讨Ce-Mg体系金属间化合物的力学性质与其晶体结构相联系的微观机制,采用基于密度泛函理论的第一性原理计算方法,系统研究了3种立方Ce-Mg体系金属间化合物CeMg、CeMg2和CeMg3的电子结构和弹性性质。计算结果表明,CeMg3有最高的体模量和剪切模量,分别为41.1GPa和30.7GPa,CeMg2的体模量和剪切模量则在3种金属间化合物中最低,分别为35.1GPa和14.0GPa。CeMg、CeMg2和CeMg3均满足立方晶系力学稳定性要求,CeMg3与CeMg为脆性材料,而CeMg2为延性材料。各向异性性质分析表明,CeMg具有很高的弹性各向异性,而CeMg2的体模量、剪切模量以及杨氏模量尽管最低,但其显示出良好的各向同性性能。计算CO-HP及电荷密度分布揭示了Ce-Mg合金体系弹性性质的变化与体系中化学成键差异密切相关,晶体中Mg-Mg键较强的材料比晶体中Ce-Mg键较强的材料有着更好的延展性。

First-principle study of elastic properties and electronic structure of Ce-Mg alloys

To explain the influence of crystal structures of Ce-Mg alloys on mechanical property,electronic structure and elastic properties of three cubic Ce-Mg binary alloys including CeMg,CeMg2,and CeMg3 were investigated using the first-principles method based on density functional theory.The calculated results show that CeMg3 has the highest bulk modulus and shear modulus of 41.1 GPa and 30.7 GPa,while CeMg2 has the lowest of 35.1 GPa and 14.0 GPa.CeMg,CeMg2,and CeMg3 meet the requirement of mechanical stability in a cubic crystal.The analysis on elastic properties indicates that CeMg and CeMg3 belong to brittle materials,and CeMg2 is ductile.And the investigation on elastic anisotropy reveals that CeMg exhibits a high degree of anisotropy.Although CeMg2 has the lowest bulk modulus,shear modulus and Young’s modulus,it shows good isotropic character.Based on the calculated COHP and charge density distribution,it can be seen that the difference in chemical bonding is responsible for the variation of elastic properties in Ce-Mg alloys.Stronger bonding between Mg-Mg in crystal can enhance the ductility of alloy.