Center for Computational Materials Science, Institute of Materials Research, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan.
J Chem Phys. 2012 Feb 14;136(6):064706. doi: 10.1063/1.3684900.
The three step auf bau of a triangular polyaromatic protrusion attached to a larger parent hexagonal shaped graphene nanodot (GND) is described and the dichotomy between intrinsic protrusion localized magnetism and parent extended zigzag edge magnetism is explored using ab initio density functional theory calculations of spin and charge distributions and geometry. Comparison of a three ring with a ten-ring protrusion-GND establishes a pattern for the magnetization of GNDs with larger protrusions and different morphology. The magnetism of the isolated protrusions arises from the mismatch in numbers of sublattice (alternant hydrocarbon) carbon atoms. In the parent, the sublattices are equivalent providing a singlet ground state and the magnetization appears only on long zigzag edges due to exchange interactions operating in a regime of reduced coulombic interactions. We demonstrate that a small protrusion can quench the magnetism of the edge to which it is attached. Concomitantly, the adjacent edges exhibit a small magnetic enhancement, while the remote edges are unperturbed. With size the protrusion can dominate its edge and exert control over the magnetization of other edges. Different multiplicities of the parent moiety were not found. These calculations provide guidance in understanding how the magnetism changes with system shape and in designing nanodots with a specific magnetization.
描述了附着在较大母体六方形状石墨烯纳米点 (GND) 上的三角形多环突出物的三步构建过程，并使用从头算密度泛函理论计算的自旋和电荷分布和几何形状来探索固有突出物局域磁化和母体扩展锯齿边缘磁化之间的二分法。三环与十环突出物-GND 的比较为具有较大突出物和不同形态的 GNDs 的磁化建立了模式。孤立突出物的磁性源于亚晶格（交替烃）碳原子数量的不匹配。在母体中，亚晶格是等效的，提供单重态基态，并且由于在库仑相互作用降低的区域中起作用的交换相互作用，仅在长锯齿边缘出现磁化。我们证明，小的突出物可以熄灭与之相连的边缘的磁性。同时，相邻边缘表现出微小的磁性增强，而远程边缘则不受干扰。随着尺寸的增加，突出物可以控制其边缘并控制其他边缘的磁化。未发现母体部分的不同倍数。这些计算为理解磁随系统形状的变化以及设计具有特定磁化的纳米点提供了指导。
