▎ 摘　　要

The effect of external static charging of graphene and its flakes are investigated by using first-principles calculations. While the Fermi level of negatively charged graphene rises and then is quickly pinned by the parabolic, nearly free electronlike bands, it moves down readily by removal of electrons from graphene. Excess charges accumulate mainly at both surfaces of graphite slab. Even more remarkable is that Coulomb repulsion exfoliates the graphene layers from both surfaces of positively charged graphite slab. The energy level structure, binding energy, and spin-polarization of specific adatoms adsorbed to a graphene flake can be monitored by charging. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573806]