Heusler合金Mn2NiAl的电子结构、 磁性质及四方变形的第一性原理

利用基于密度泛函理论的第一性原理, 计算Mn₂NiAl的晶体结构、 四方变形、 磁性、 电子结构和压力响应. 计算结果表明: Mn2NiAl在立方奥氏体相的平衡结构为铁磁态MnMnNiAl型结构, 其中Mn原子占据A和B不等价晶位; 在由立方结构向四方结构的变形中, 在c/a≈1.24处存在一个稳定的马氏体相; 在奥氏体相和马氏体相下, Mn原子对Mn2NiAl总磁矩的贡献最大,  Mn(A)和Mn(B)原子磁矩的值不等并呈反平行耦合, 且Mn(A)-d和Mn(B)-d的投影态密度在费米面附近交叠均较少,

First-Principles of Electronic Structure and Magnetic Properties and Tetragonal Distortion of Heusler Alloy Mn2NiAl

Crystal structure,tetragonal distortion,magnetism,electronic structure and pressure response of Mn2NiAl were calculated by means of first-principles method based on the density functional theory.The calculation results show the equilibrium structure of Mn2NiAl in the cubic austenitic phase is the MnMnNiAl structure with Mn atoms occupying A and B non-equivalent positions.In the process of transform from a cubic to a tetragonal structure,Mn2NiAl alloys exhibit a stable martensitic phase in c/a≈1.24.In both the austenite and martensite phases,the contribution of Mn atoms to the total moments for Mn2NiAl is the largest,the magnetic moments of Mn(A) and Mn(B) atoms are inequality and antiparallel couple.The direct d-d exchange interactions between Mn(A) and Mn(B) atoms are weak because of the small overlap of d-projected DOS of Mn(A) and Mn(B) atoms nearby the Fermi level,but the intra-atomic interactions in Mn atoms are strong,this is the reason why the Mn2NiAl alloys show ferrimagnetism.