Band gaps in armchair-edge graphene nanostrips

First-principles calculations have shown that all graphene nanostrips terminated with hydrogen atoms exhibit band gaps at the Fermi level. In the case of armchair-edge nanostrips, the calculations contradict a first-nearest-neighbor tight-binding prediction that one third of these nanostrips should be metallic. At the one-electron level, at least two independent causes for the band gaps in these nanostrips have been suggested, namely lattice distortion and long-range interactions. In this presentation, we present theoretical calculations of arbitrary armchair-edge nanostrips. The model, which includes distortion of edge atoms and third-nearest-neighbor interactions, leads to band gaps and band structures which are in good agreement with those obtained from our first-principles calculations.