▎ 摘　　要

Adsorption of an O-2 molecule on a graphene sheet with and without a Stone-Thrower-Wales (STW) defect is examined by the density-functional theory calculations. The presence of an O-2 molecule or a defect breaks the usual symmetry of graphene, and thus the electronic structure is examined in detail by the three-dimensional plot of the energy surfaces of the spin-dependent two-dimensional band structure. The energetics have clarified that O-2 physisorption is possible for graphene with and without STW defects. The O-2 physisorption does not trigger opening of the band gap around K point, while it induces holes in the majority-spin pi band of graphene. The number of holes induced by one O-2 molecule is calculated from the density of states (DOS) as 0.0087 holes/O-2 for defect-free graphene and 0.0241 holes/O-2 for graphene with STW defects. It is clear that the hole doping by O-2 physisorption is enhanced by STW defects. (C) 2013 Elsevier Ltd. All rights reserved.