▎ 摘　　要

First-principles calculations have been employed to investigate structures and electronic properties of oxidized graphene. Based on the calculations of binding energy, the stable configurations of single and double O atoms adsorbed on graphene have been firstly explored. Subsequently, two types of geometrical structures of oxidized graphenes with O/C ratio of 1/2 have been discovered, and both exhibit rectangular symmetries with all C atoms in sp(3) hybridizations. By using ab initio molecular-dynamics simulations, it is demonstrated that these oxidized graphenes could be maintained at room temperature. Besides, electronic band structures show that both two oxidized graphenes are semiconductors with wide direct band gaps at the Gamma-point. The characteristics of atomic orbital contributions at valence band maximum and conduction band minimum have been analyzed. Our study suggests the possibility of opening a band gap of graphene by oxidizations and may provide the ground state of oxidized graphene. Copyright (c) EPLA, 2014