Hg_2CuTi型Mn_2NiGe合金的电子结构、磁性对压力、四方变形的响应

The responses of electronic structure and magnetism to pressure and tetragonal distortion in the Hg_2CuTi-type Mn_2NiGe alloy

运用基于密度泛函理论的第一性原理方法,研究了Hg_2CuTi型Mn_2NiGe合金的电子结构对外加压力的响应以及Mn_2NiGe的电子结构、磁性对四方变形的响应.结果表明:i)随着外加压力的增加,因Ni、Mn原子间距的减小而导致杂化程度的增强,使得态密度整体向低能区域移动,同时,态密度幅度整体略有减小;ii)在由奥氏体相到马氏体相的变形中,同样因Ni、Mn原子间距的减小而导致杂化程度的增强,占据态的态密度向低能区域移动,体系的能量降低,同时,成键态向低能方向移动,反键态向高能方向移动,能带变宽,成键作用加强,最终导致在马氏体相中的稳定性增大;iii)在四方变形过程中,Mn_2NiGe总磁矩的变化主要由Ni原子磁矩的变化所产生.

By the first-principles method based on the density functional theory, we investigate the responses of electronic structure and magnetism to pressure and tetragonal distortion in the Hg2CuTi-type Mn2NiGe alloy. The results show that： i） With increasing the impressed pressure, the hybridization degree will be enhanced due to the reduction of the Ni--Mn interatomic distance, which leads to the moving to lower energy and the diminishing of the amplitude for the density of states, ii） In the process of transformation from the austenite phase to the martensite phase, the hybridization degree will also be enhanced due to the reduction of the Ni--Mn interatomic distance, the density of states of the occupied state moves to the lower energy and the system energy decreases. Meanwhile, the bonding state moves to the lower energy and the antibonding state moves to the higher energy, the energy band becomes broader and the bonding interaction becomes stronger, which lead to the increasieg of the stabilization of martensitic phase, iii） In the process of tetragonal distortions, the change of total magnetic moment is mainly induced by the change of magnetic moment of Ni atom.