作　　者： ; ; ; ; ; ; (邓军权）;

机构地区： 重庆师范大学物理与电子工程学院

出　　处： 《科学通报》 2015年第9期830-837,共8页

摘　　要： 采用基于密度泛函理论的第一性原理计算方法,对纯LiMgN,Cu掺杂LiMgN,以及Li过量和不足时Cu掺杂LiMgN体系进行几何结构优化,计算并分析体系的电子结构、半金属性、形成能及光学性质.结果表明,Cu掺入使体系产生自旋极化杂质带,表现出半金属性,且体系性质受Li计量数的影响.当Li不足时体系的杂质带宽度增大,半金属性增强,净磁矩增大,同时体系的形成能降低,居里温度提高.而当Li过量时,体系半金属性消失,但带隙值减小,导电能力增强.通过比较光学性质发现,Cu掺入后体系在低能区出现新的介电峰,且当Li不足时介电峰增强,同时复折射率函数也发生明显变化,体系对低频电磁波吸收加强. Using first-principles density functional theory based on the full potential linearized augmented plane wave method and the local spin density approximation（LSDA）, the geometric structures of pure Li Mg N, Cu-doped Li Mg N, and Cu-doped Li Mg N with either excess Li or Li deficiency are optimized, and their electronic structures, half-metallic properties, formation energies and optical properties are calculated. The results indicate that Cu doping makes the Cu3 d states hybridize with the Li2s and N2p states simultaneously, and this leads to sp-d orbital hybridization. The resulting system produces spin polarization impurity bands, displays half-metallic behavior and has a net magnetic moment. Li（Mg0.9375Cu0.0625）N is still a direct band gap semiconductor like Li Mg N. The bottom of its conduction band and the top of its valance band are both at the G point in the Brillouin zone. The band gap of the material is 2.41 e V, which is slightly narrower than the value of 2.47 eV for Li Mg N. There are a total of six impurity bands in the band gap. Three of these bands are in the spin-up band, and the other three are in the spin-down band. In the spin-down band, the Fermi level goes through the impurity bands, and thus the material shows half-metallic properties. The half-metallic energy gap is 0.09 eV. The strong sp-d orbital hybridization causes the energy level to split, and the t2 g energy level of the Cu3 d state electrons in the spin-down band is pushed above the Fermi level, which leads to half-filled states. The number of spin-up electrons is slightly more than that of the spin-down electrons, and the Li（Mg0.9375Cu0.0625）N system has a 1.04μв net magnetic moment. The properties of the Li-deficient or Li-excess systems are affected by the stoichiometric number of Li in each case. In the Li-deficient compounds, the Li vacancies strengthen the sp-d orbital hybridization, and make the impurity band width, the half-metallic properties, the net magnetic moment, and the Curie temperature increase, while t

关 键 词： 掺杂 电子结构 光学性质 第一性原理

领　　域： [理学] [理学]