单层正三角锯齿型石墨烯量子点的电子结构和磁性

Electronic structure and magnetism of single-layer trigonal graphene quantum dots with zigzag edges

采用基于密度泛函理论的广义梯度近似(GGA),对不同尺寸(N=2—11)的单层正三角锯齿型石墨烯量子点(ZN-GNDs)的结构进行优化,得到与实验数据较好符合的晶格常数,进一步计算得到不同尺寸下体系的自旋多重度、磁矩、电子态密度以及自旋电子密度.结果表明:所有体系都呈现金属性,在尺寸较小的体系中量子尺寸效应对电子结构的影响比较明显;与单层石墨烯片一样,sp2杂化作用和非键态电子在量子点中仍起到非常重要的作用;费米能级上有自旋向上的电子分布,体系的自旋多重度和总磁矩随着体系尺寸的增大而增大,分析认为总磁矩主要来自于锯齿形边界上碳原子的2p轨道上非键态电子的贡献.本工作对基于三角锯齿型石墨烯量子点的器件设计具有指导意义.

The geometry,spin multiplicity,magnetic moment,electronic density of states and the spin density of single-layer trigonal graphene quantum dots with zigzag edges have been systematically investigated using density functional theory with the generalized gradient approximation under different sizes. The calculated results such as lattice constants are in good agreement with experimental data and indicate that the system behaves like metal,while the electrons with up spins occupy the Fermi energy. The influence of quantum size effect is remarkable in the system of small size. It is also found that the sp2 hybridization and nonbonding electrons play an important part in the single-layer trigonal graphene quantum dots,just like in graphene. The spin multiplicity and magnetic moment of the system increase with the increase of the system size. Based on our calculation,the total magnetic moment of the system mainly comes from the nonbonding electrons on the 2p orbital of the zigzag boundary. Our calculation may be helpful in designing devices based on trigonal graphene quantum dots.