  We present the results of ab-initio density functional theory based
calculations of the stability and reconstruction of zigzag edges in triangular
graphene quantum dots. We show that, while the reconstructed pentagon-heptagon
zigzag edge structure is more stable in the absence of hydrogen, ideal zigzag
edges are energetically favored by hydrogen passivation. Zero-energy band
exists in both structures when passivated by hydrogen, however in case of
pentagon-heptagon zigzag, this band is found to have stronger dispersion,
leading to the loss of net magnetization.
