石墨烯量子点的磁性及激发态性质

利用密度泛函理论在B3LYP/6-31G(d)基组水平上研究了具有zigzag边界的石墨烯量子点,结果表明不同大小的石墨烯量子点的基态都是具有磁性的自旋三重态.其磁性一方面来源于zigzag边界上占有凸出位置的碳原子,另一方面来源于带有孤对电子的碳原子.从整体上看,除6b结构外,其他结构的能隙随着苯环数量的增加逐渐减小,而附加电荷却使体系能隙明显减小.用含时密度泛函理论(TD-DFT)对能隙为3.83 eV的由六个苯环排列成的三角形结构进行了激发态的计算,发现第十七激发态强度最大,能量为3.93 eV,对 关键词： 石墨烯量子点 磁性 能隙 激发态

Magnetic properties and excited states of the graphene quantum dots

We use the density functional theory B3LYP/6-31G(d) to study the graphene quantum dots with zigzag edges. The result shows that the ground states of different size graphene quantum dots are all ferromagnetic spin-triplet states. The magnetic properties orignate both from the boundary carbon atom occuping protruding position, and from the carbon atom with unpaired electron. On the whole, the energy gap of other structures decreases with the increase of the number of benzene rings as excepted for the structure of 6b, and the system energy gap decreases significantly by the added charges. In addition, using time-dependent density functional theory (TD-DFT), the excited states of the triangular structure composed of six carbon rings which have an energy gap is 3.83 eV are calculated, and the results show that the 17th excited state has the greatest excitation strength, the excitation energy is 3.93 eV, corresponding to a wavelength of 315.8 nm, close to experimental result.