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Calculation of Electronic Structures of Graphene Nanoflakes by Hückel Molecular Orbital Method: Exploration of the Shape, Size, and Edge Effects KCI 등재 SCOPUS
pp.620-632
The electronic structures of graphene nanoflakes (GNFs) were estimated for various shapes, sizes, symmetries, and edge configurations. The Hückel molecular orbital (HMO) method was employed as a convenient way of handling the variety of possible GNF structures, since its simplicity allows the rapid solution of large system problems, such as tailoring optoelectronic characteristics of molecule containing large number of carbon atoms. The HMO method yielded the electronic structures with respect to the energy state eigenvalues, with results comparable to those obtained by other approaches, such as the tightbinding method reported elsewhere. The analyses included the consideration of various types of edge configurations of 68 GNF systems grouped by their geometric shape, reflecting symmetry. It was inferred that GNFs in the small length scale regimes, below 1 nm, which are effectively small polycyclic aromatic hydrocarbon molecules, exhibit the optoelectronic characteristic of quantum dots. This is due to the widely spaced discrete energy states, together with large energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). With increasing size this arrangement evolves into graphene-like ones, as revealed by the narrowing HOMO-LUMO gaps and decreasing energy differences between eigenstates. However, the changes in electronic structure are affected by the symmetries, which are related to the geometric shapes and edge configurations.
1. Introduction
2. Numerical Procedure
3. Results and Discussion
4. Conclusion
Acknowledgement
References
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