CoSi合金的磁性和光学性质的第一性原理研究

First-principles study on magnetic and optical properties of CoSi alloy

采用第一性原理的局域自旋密度近似和在位库伦能修正(LSDA+U)的计算方法,结合广义梯度近似下的赝势平面波方法,计算了CoSi合金的磁性和光学性质。计算结果显示在费米能级附近,CoSi合金的上自旋能级与下自旋能级相互交叠,出现了明显的自旋极化现象,并且自旋态密度都穿过费米能级,表明CoSi合金具有金属特征。磁性计算结果表明CoSi合金具有铁磁性,磁性主要来源于Co原子3d轨道电子的贡献。特别是采用LSDA+U修正方法发现,当位库伦修正值增加到6.6eV时,CoSi合金体系的几何参数与实验值完全吻合,表明位库仑能U值的大小对CoSi合金的原子磁矩以及磁性原子的能级分布影响较大。同时,光学吸收谱计算结果表明,随着位库仑能U值的增大,CoSi合金的吸收峰在低能区发生红移,在高能区发生蓝移。以上结果表明,CoSi合金是一种很好的磁光导电材料。

The magnetic and optical properties of CoSi alloy were calculated by using the first-principles calculation of local spin density approximation with Coulomb energy correction（LSDA＋U） based upon the plane wave pseudo-potential method of the generalized gradient approximation（GGA）. The calculated results show that the upward and downward spin energy level of CoSi alloy overlap near the Fermi level, an obvious spin polarized phenomenon occurrs and the spin density of states crosses over the Fermi level, which demonstrates that CoSi alloy owns the metal characteristics. The magnetic studies indicate that CoSi alloy has some magnetism which is mainly derived from the contribution of Co 3d orbit electrons. Particularly, after employing the local spin density approximation with U correction, it is observed that when the Coulomb value increases to 6.6 e V, the geometry parameters are consistent with the experimental values, this shows that the coulomb energy U has a large impact on the atomic magnetic moment and energy level distribution of magnetic atoms. Meanwhile, the absorption spectrum manifests that with increase of the coulomb energy U, the absorption peak shifts to the red and the blue orientation at low and high energy region, respectively. The above results show that CoSi alloy is a good kind of magnetic, optical and conductive material.