基于密度泛函理论的L2_1型Ni_2MnGe第一原理计算

First-principles calculations on Ni_2MnGe of L2_1-type structure with density functional theory

运用MaterialsStudio6.0程序CASRTEP软件包建立L21型Ni2MnGe单胞和1×1×5的Ni2.25Mn0.75Ge超胞模型,采用GGA-PBE-TS近似,得出能带结构和态密度曲线。由Ni2MnGe单胞的能带结构和态密度图可以看出自旋向上和自旋向下的能带都没有出现带隙,说明Ni2MnGe单胞具有金属性,在费米能级附近不同自旋能带具有明显差别,从而导致Ni2MnGe具有较大磁性;通过分析1×1×5的Ni2.25Mn0.75Ge超胞的能带结构和态密度图可以得到同样的结论,即Ni2.25Mn0.75Ge具有金属性,在费米能级附近不同自旋能带具有明显差别,从而导致Ni2MnGe具有较大磁性。2种晶体中Ni原子自旋向上和自旋向下的态密度占据量几乎相同,因此Ni原子的磁矩很小,而Mn原子d轨道的电子几乎全部局域在自旋向上的态密度中,因此Mn原子磁矩较大。Ni2.25Mn0.75Ge中Ni(A)与Mn存在p-d杂化,比Ni2MnGe中p-d杂化作用更强,这是由于Ni替换了Mn的缘故。

The band structure and density of states （DOS）properties were calculated by CASTEP codes of MaterialsStudio6. 0, which were built as Ni2 MnGe unit cell and Ni2.25 Mn0. 75 Ge 1 X 1 X 5 supercell, and by using generalized gradientapproximation（GGA）. By the NizMnGe unit cell of band structure and density of state, we can see that the spin up andspin down energy band does not appear gap, indicating that Ni2MnGe is metal, different spin near the Fermi level bandhaving significantly different, resulting in having a large magnetic Ni2MnGe; By analyzing the energy band structure anddensity of states Niz2 Mn0. 75 Ge supercell of 1 x1 x5 can get the same conclusion, namely Ni2. 25 Mn0. 75 Ge with a metallicproperty, and in the vicinity of the Fermi level can bring different spin significantly different, resulting in Ni2MnGehaving a large magnetic. Two crystals of Ni atoms in the spin-up and spin-down state density occupy almost the sameamount, so the magnetic moment of Ni atom is very small, and d type orbital electronic of Mn atoms almost in thedensity of state in spin-up, so the magnetic moment of Mn atom in larger. Ni2. 25 Mno. 75 Ge in Ni （A） and the presence of p-d Mn hybrid, p-d hybridization effect is stronger than NizMnGe, this is due to the replacement of Ni Mn sake.