【摘要】 采用基于密度泛函理论的第一性原理框架下的投影扩充波函数(PAW)方法,研究了Heusler合金Ni2Mn Ga马氏体相变的微观电子结构机理.结果表明:Ni2Mn Ga发生马氏体相变时,其晶体发生了自正八面体结构朝z轴拉长型八面体结构的畸变.此畸变源自于由Ni的eg轨道电子的非均匀排布所引发的强带Jahn–Teller效应,其发生的机制是:通过孤对电子由dx2-y2轨道转移到dz2轨道,导致x、y方向的配体内移,z方向的配体外移,从而使dx2-y2、dxy能级升高,及dz2、dyz、dxz能级降低,消除和降低能级的简并度,体系能量降低,体系畸变到一个更稳定的状态(马氏体相).更多还原

【Abstract】 The mechanism of microcosmic electronic structure of martensitic transformation in Heusler alloy Ni2 Mn Ga is researched by the projected augmented wave method based on the first- principles of density functional theory. The results show that it generates distortion from regular octahedron structure to elongated octahedron structure with martensitic transformation in Ni2 Mn Ga. This distortion is derived from a strong band Jahn –Teller effect involving non- uniform distribution of electrons of egorbit of ionic Ni,its mechanism is: the ligands pointing to x and y directions move inward and the ligands pointing to z directions move outward due to unpaired electrons transfer to dz2 orbit from dx2- y2 orbit,this can lead to the eliminate degeneracy of energy level derived from the rising of energy levels of dx2- y2 and dxy,and the lowering of energy levels of dz2,dyzand dxz,and thus the system energy decreases,the system changes to the stabilized martensitic phase.更多还原