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采用基于DFT理论的第一性原理计算方法对石墨烯吸附氢的磁性进行研究。首先对石墨烯量子点进行磁性的研究,研究表明边缘用氢钝化的石墨烯量子点所表现出的磁性和石墨烯量子点的切割形状紧密相关,切割形状为矩形的石墨烯量子点表现出反铁磁的性质,切割形状为三角形的石墨烯量子点表现出铁磁的性质。其次对石墨烯晶格吸附氢栅和氢探针所引起的自旋磁性进行计算研究,结果表明通过氢栅的吸附可以改变石墨烯的几何结构和能带结构,石墨烯的形状由二维的平直结构变为三维的起伏结构,石墨烯的带隙从零变为0.214 e V。最后研究氢探针对氢栅的影响,发现氢探针能够改变氢栅附近自旋密度分布,引起自旋干涉现象。我们计算了4个典型的位置A_1、A_2、B_1、B_2,发现不同的探针吸附位置引起不同的自旋干涉,氢栅的自旋密度分布与碳原子自旋密度分布趋势一致,但碳原子的自旋磁矩比氢栅的自旋磁矩大三倍,并且氢探针越靠近氢栅,自旋的干涉效应越明显。这些性质有助于石墨烯在自旋半导体器件、自旋开关等领域中的应用。
The first principle calculation method based on DFT theory was used to study the magnetism of graphene hydrogen adsorption. First of all, the magnetic properties of graphene quantum dots have been studied. The results show that the edges of the graphene quantum dot with hydrogen passivation are closely related to the cutting shape of the graphene quantum dot. The graphene quantum dots with a rectangular cutting shape show Anti-ferromagnetic nature, the cutting shape of the triangular graphene quantum dots exhibit ferromagnetic properties. Secondly, the spin magnetic properties induced by the hydrogen grid and the hydrogen probe are adsorbed on the graphene lattice. The results show that the graphene geometry and band structure can be changed by the adsorption of hydrogen grid. The flat structure becomes a three-dimensional undulating structure, and the bandgap of graphene changes from zero to 0.214 eV. Finally, we study the influence of hydrogen probe on the hydrogen grid and find that the hydrogen probe can change the spin density distribution near the hydrogen grid and cause spin-interference phenomenon. We calculated four typical locations A_1, A_2, B_1, B_2 and found that different probe sites caused different spin interferences. The spin density distribution of the hydrogen grid is consistent with that of the carbon atom spin density distribution. However, the carbon atom The spin magnetic moment is three times larger than the spin magnetic moment of the hydrogen grid, and the closer the hydrogen probe is to the hydrogen grid, the more obvious the spin interference effect. These properties contribute to the application of graphene in spin-on semiconductor devices, spin-switches and the like.