Electronic superstructures on the graphite surface studied by first-principles calculations

We present results of a first-principles study of the graphite surface in the presence of defects. Our calculations, based on density functional theory, show superstructures of periodicity (root 3 x root 3) in the electronic structure of the surface. In good agreement with STM experiments, these superstructures show a variety of patterns with their intensity decaying away from the defect. Two kind of defects were considered: metallic adatoms absorbed on graphite, and vacancies in the surface lattice. Similar results were found in both cases. Our results give strong support to the idea that these superstructures are due to purely electronic effects, and do not correspond to any atomic reconstruction of the graphite surface. (C) 1997 Elsevier Science B.V.