The changes of crystal structure, magnetic structure, electronic structure in the martensitic phase transition for magnetic shape memory alloy Mn2NiGe are calculated by first-principles method. The results show that in the martensitic phase transition for Mn2NiGe, there is produced a Jahn-Teller distortion, in which the c-axis becomes longer but a-axis and b-axis turn shorter, form- ing an elongated octahedral geometry. There is a significant change in magnetic moment for Mn ion in the centre of octahedron, but a little change happens to the Ni and Ge ions that are regarded as a ligand. The energy levels of eg and t2g are split by redistributing the density of states for d electrons and so opening a pseudogap near the fermi energy due to lattice distortion.%运用第一性原理的方法，计算磁性形状记忆合金Mn2NiGe的晶体结构、磁结构、电子结构在马氏体相变中的变化．结果表明：MnzNiGe在发生马氏体相变时，产生了c轴拉长而a和b轴缩短的Jahn．Teller畸变，形成一个由两根长键和四根短键组成的拉长的八面体；伴随Jahn—Teller畸变，处于八面体中心的Mn离子的磁矩发生了显著的变化，而作为配体的Ni和Ge离子的磁矩基本不变；Jahn—Teller效应中Mn离子的eg和t2g能级的分裂，源自于晶体畸变所产生的配位场的改变，导致Mn离子d电子态密度的重新分布，从而在费米能级两侧打开一个赝能隙．
展开▼
