Electronic structure and aromaticity of large-scale hexagonal graphene nanoflakes.

摘要: With the help of recently developed SIESTA-pole (Spanish Initiative for Electronic Simulations with Thousands Atoms) - PEXSI (pole expansion and selected inversion) method [L. Lin, A. Garcia, G. Huhs, C. Yang, J. Phys.: Condens. Matter 26, 305503 (2014)], we perform Kohn-Sham density functional theory calculations to study stability electronic structure hydrogen passivated hexagonal graphene nanoflakes (GNFs) up 11 700 atoms. We find properties GNFs, including their cohesive energy, edge formation highest occupied molecular orbital-lowest unoccupied orbital energy gap, states, aromaticity, depend sensitively on type edges (armchair (ACGNFs) zigzag (ZZGNFs)), size number electrons. observe that, due edge-induced strain effect in ACGNFs, large-scale ACGNFs’ decreases as increases. This trend does not hold ZZGNFs presence many states ZZGNFs. that gaps E g GNFs all decay respect 1/L, where L is GNF, a linear fashion. But increases, exhibit more localized states. believe these makes gap decrease rapidly. In particular, when larger than 6.40 nm, metallic characteristics. Furthermore, aromatic structures appear only whether system has 4N or + 2 electrons, N an integer. © 2014 AIP Publishing LLC .[ http://dx.doi.org/10.1063/1.4902806]