Identification of 5-7 defects in a copper oxide surface.

A topological defect in a Cu(2)O surface oxide grown on Cu(111) has been identified. Using scanning tunneling microscopy, we observed the formation of pentagonal and heptagonal rings within the Cu(2)O surface oxide. These structures break the symmetry of the hexagonal oxide surface and are a consequence of the presence of oxygen vacancies in the Cu(2)O surface. We propose that the pentagonal and heptagonal rings are formed through the rotation of a -O-Cu-O- chain in a manner similar to the Stone-Wales transformation. The proposed transformation is supported by the results of density functional theory calculations.