Effect of edge reconstruction and passivation on zero-energy states and magnetism in triangular graphene quantum dots with zigzag edges

We present the results of ab initio calculations of the effect of reconstruction and passivation of zigzag edges on the electronic and magnetic properties of triangular graphene quantum dots. We find that, similarly to nanoribbons, hydrogen-passivated ideal zigzag edges are energetically favored over the pentagon-heptagon zigzag. However, the reconstructed edge is more stable in the absence of hydrogen, thus, delayed passivation with H may lock the dot in such an unfavorable configuration. Both hydrogen-passivated edge morphologies lead to a band of states at the Fermi level. Unlike in nanoribbons, this quasidegenerate band results in net spin polarization for structures with zigzag edge of all sizes studied here. For triangular dots with pentagon-heptagon zigzag edge, a larger width of the zero-energy band is predicted, leading to the loss of net magnetization.