(a) Two possible representations of the zero-energy TB wavefunctions for the octagonal carbon ring. Filled and empty circles mean positive and negative values of the wavefunction; no circle means that the wavefunction is exactly zero. (b), (c) Schematic views showing how the 8R and 8N octagons are connected to the voids V8R and V8N, respectively. Filled and empty circles indicate the void-edge nodes corresponding to different sublattices.
