Optical Absorption Spectrum of Small Graphene Fragments with Topological Defects

Energy spectra of small graphene fragments with and without topological defects (vacancies, nanopores and Stone–Wales defects) are obtained using the Hubbard model based on the approximation of static fluctuations. Modeling of optical absorption spectra is performed for both defect-free and defective small graphene fragments of the lattice. The analysis is given to optical absorption spectra changing with increasing number of vacancies. It is shown how the energy gap depends on the defect configuration and concentration.