含空位二维六角氮化硼电子和磁性质的密度泛函研究

Density functional study on the electronic and magnetic properties of two-dimensional hexagonal boron nitride containing vacancy

基于密度泛函理论的第一性原理计算,研究了含B原子空位(VB),N原子空位(VN),以及含B N键空位(VB+N)缺陷的二维氮化硼(h-BN)的电子和磁性质.在微观结构上,VB体系表现为在空位附近的N原子重构成等腰三角形,VN体系靠近空穴的B原子形成等边三角形,VB+N体系靠近空穴处的B和N原子在h-BN平面上重构为梯形.三种空位缺陷都使h-BN的带隙类型从直接带隙转变为间接带隙.VB体系的总磁矩为1.0μB,磁矩全部由N原子贡献.其中空穴周围的三个N原子磁矩方向不完全一致,存在着铁磁性和反铁磁性两种耦合方式.对于VN体系,整个晶胞内的总磁矩也为1.0μB,磁矩在空穴周围区域呈现一定的分布.

According to density functional first-principles calculations, we study the electronic and magnetic properties of two-dimensional h-BN containing lattice vacancies： B atom vacancy （VB）, N atom vacancy （VN） and BN pair vacancies （VBN）. In microstructures, the neighbored N atoms around vacancy in VB system are constructed into an isosceles triangle;the neighbored B atoms around vacancy in VN system are constructed into an equilateral triangle;and the neighbored atoms around BN pair vacancies are constructed into a keystone. The calculations on band structures and density of states show that the significant spin polarization exists in two-dimensional h-BN containing single vacancy defects, while the BN pair vacancy system exhibits non-spin polarization. Three kinds of vacancy defects make the band gap change from direct band gap to indirect band gap. For the VB system, the total magnetic moment is 1.00 μB , due to the contribution from the neighbored N atoms around vacancy. The directions of magnetic moment in three neighbored N atoms around vacancy are different. Among them, ferromagnetic and anti-ferromagnetic coupling are coexisting. For the VN system, the total magnetic moment in the entire calculated supercell is also 1.00 μB and presents a certain distribution in the area around the vacancy.