第一主族元素(Li,Na,K)和第二主族元素(Be,Mg,Ca)掺杂二维六方氮化硼单层的第一性原理计算研究

First principles caculations of h-BN monolayer with groupⅠA/ⅡA elements replacing B as impurities

采用基于密度泛函理论的第一性原理计算方法研究了第一、第二主族元素取代六方BN单层中的B的几何结构、磁性性质和电子结构.研究发现,掺杂的BN单层出现明显的自旋极化特性.对Li,Na,K而言,掺杂后超胞的总磁矩为2μB,对Mg,Ca而言,超胞的总磁矩为1μB,磁矩主要局域在与杂质原子最近邻的N原子上.而对于Be,超胞的总磁矩为0.705μB,磁矩分散在所有的N原子上.对于6种掺杂情况,给出了相应的自旋密度图.掺杂体系产生明显的杂质能级,给出了总态密度和局域投影态密度等结果,分析了杂质能级的产生.发现Mg和Ca掺杂体系的态密度具有明显的半金属特性.

Using the first principles calculations based on the density-functional theory, we study the geometric structures, magnetisms, and electronic structures of h-BN monolayer with group IA/IA elements （Li, Na, K, B, Mg and Ca） replacing B as impurities. It is shown that the nonmagnetic substitutional impurities can induce spin polarization in nonmagnetic BN monolayer. For Li, Na and K impurities, the total magnetic moment of the supercell is 2μB; for Mg and Ca, it is 1 μB. The magnetic moments are mainly localized on the nearest neighbor N atoms. The magnetic moment of the supercell with Be impurity is 0.705 μB, distributed over all N atoms. Spin polarized densities of states are presented, including total density of states and orbital-projected partial density of states. The origin of local magnetic moments and impurity energy level are explained. It is also found that the Mg and Ca doped systems are half metallic.