  The energy spectrum and electronic density of states (DOS) of zigzag graphene
nanoribbons with edges reconstructed with topological defects are investigated
within the tight-binding method. In case of the Stone-Wales zz (57) edge the
low-energy spectrum is markedly changed in comparison to the pristine zz edge.
We found that the electronic DOS at the Fermi level is different from zero at
any width of graphene nanoribbons. In contrast, for ribbons with heptagons only
at one side and pentagons at another one the energy gap at the Fermi level is
open and the DOS is equal to zero. The reason is the influence of uncompensated
topological charges on the localized edge states, which are topological in
nature. This behavior is similar to that found for the structured external
electric potentials along the edges.
