Ti-Ni金属间化合物电子结构与力学性质的第一性原理计算

First-principles calculations of electronic structure and mechanical properties of Ti-Ni intermetallic compounds

采用基于密度泛函理论(DFT)的第一性原理赝势平面波方法,计算Ti-Ni合金系中TiNi、Ti_2Ni和TiNi_3金属间化合物的平衡晶格常数、生成焓、内聚能、力学性质、德拜温度和电子结构。计算结果表明:TiNi、Ti_2Ni和TiNi_3金属间化合物均具有热力学稳定性且容易合金化生成,合金形成能力由强到弱的排序为TiNi_3、TiNi、Ti_2Ni;3种金属间化合物的晶体结构在能量上和力学上都是稳定的,结构稳定性由大到小排序依次为Ti_2Ni、TiNi、TiNi_3;TiNi和Ti_2Ni为延性相(延展性Ti_2Ni大于TiNi的),TiNi_3的延展性较差;3d电子是TiNi、Ti_2Ni和TiNi_3金属间化合物的最主要的成键电子,在这3种金属间化合物中,随着Ni相对含量的增加,平均成键电子数增多,共价键的比例增加,化学键的强度增强,金属性减弱,从而使得其弹性模量、硬度和德拜温度均逐渐升高。

The crystal structure, enthalpy of formation, cohesive energy, mechanical properties, Debye temperature and electronic structure of TiNi, Ti2Ni and TiNi3 intermetallic compounds were calculated by using first-principles ultrasoft pseudo-potential approach of the plane wave based on density functional theory （DFT）. The calculated results show that three intermetallic compounds all have thermodynamic stability and are easy to form alloy. TiNi3 has the strongest alloys forming ability. The crystal structures of those intermetallic compounds are stable in energy and mechanics, the stability in descending order are as follows： Ti2Ni, TiNi, TiNi3. TiNi and Ti2Ni are ductile, and the ductility of Ti2Ni is significantly higher than that of TiNi. TiNi3 has a poor ductility. The 3d electronics are the mainly bonding electrons. As the increase of relative amounts of Ni in those intermetallic compounds, the average bonding electrons are growing, the strength of chemical bonds enhance, the metallicity weakens. This leads to gradually increase of the elasticity modulus, hardness and Debey temperature.