过渡金属掺杂MgH_2的结构和磁性的第一性原理研究

Crystal structure and magnetic properties of transition metal-doped MgH_2 semiconductors by first principles

为研究过渡金属掺杂对氢化物铁磁性的影响,采用密度泛函理论的第一性原理平面波赝势方法,以Mg H2为基本材料,以过渡金属(V、Cr、Mn、Fe、Co和Ni)元素替代2×1×2超晶胞中的Mg原子建立掺杂模型Mg1-xMxH2(M=V、Cr、Mn、Fe、Co和Ni),并计算模型自旋极化的磁性、能带结构和态密度等性质.结果表明:与Mg H2中的Mg—H键相比,过渡金属M(M=V、Cr、Mn、Fe、Co和Ni)—H间的相互作用明显增强,造成Mg—H间强烈的离子键和部分共价键的相互作用随着过渡金属的掺杂而被削弱.掺杂体系中,V和Cr是受主杂质,而Mn、Co和Ni体系中,自旋极化率相对较低,且穿过费米能级的子带的斜率较低.研究表明过渡金属(V、Cr、Mn、Co和Ni)掺杂的Mg H2体系虽然可以导电,但电导率较小,具有比较稳定的半金属性.

In order to study the effect of transition metal doped on ferromagnetic properties of hydride, with MgH2 as the ba- sic material, Mg1-xMxH2（M = V,Cr,Mn,Fe,Co,Ni） doped model was established by substituting transition metal（M = V,Cr, Mn,Fe,Co,Ni） elements for the magnesium atoms in 2×1 × 2 supereell model using first-principles pseudopotential plane wave method which was based on density functional theory, and the properties of the model were calculated, such as spin- polarized magnetism, band structures and density of states. The results show that interactions between transition metal M（M = V, Cr, Mn, Fe, Co, Ni） elements and H are significantly enhanced compared with Mg--H in MgH2, which weaken the strong interactions of ionic bonding and some covalent bonding between Mg and H. V and Cr are acceptor impurity in the doped system, and the spin polarization rate and the slope of sub-bands through the Fermi level are both relatively lower in Mn, Co and Ni system. The doped system can conduct electricity with small electrical conductivity, which has relatively sta- ble half-metallicity.