▎ 摘　　要

We study electronic and geometric structures of the fluorine adsorbed graphene sheet using an ab initio pseudopotential method. We find that the fluorine atom forms covalent bond with the carbon atom and locally terminates the pi -states on the graphene sheet. The charge distribution exhibits a typical root3 x root3 structure near the Fermi energy. This means that the doped fluorine atom acts as a local defect on the pi -electron network of a graphene sheet.