▎ 摘　　要

By performing density functional theory calculations, we studied the quantum confinement in charged graphene quantum dots (GQDs), which is found to be clearly edge and shape dependent. It is found that the excess charges have a large distribution at the edges of the GQD. The resulting energy spectrum shift is very nonuniform and hence the Coulomb diamonds in the charge stability diagram vary irregularly, in good agreement with the observed nonperiodic Coulomb blockade oscillation. We also illustrate that the level statistics of the GQDs can be described by a Gaussian distribution, as predicted for chaotic Dirac billiards. The charge stability diagram (left) and the Gaussian distribution of the width of the Coulomb diamonds (right), indicating the nonperiodic Coulomb blockade oscillation in GQD due to quantum confinement. ((c) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)