A scanning-tunneling-microscopy study for a surface formed by the chemisorption of oxygen on Cu(100) and displaying a (2 √2 × √2 )R45° low-energy-electron-diffraction (LEED) pattern shows the expected rotationally related domains but no unambiguous evidence for coexisting regions of c(2×2) symmetry. There is a clear pairing of atomic rows, but a low corrugation (≲0.2 Å). These features are consistent with results from a new LEED multiple-scattering analysis applied to six diffracted beams for normal incidence. The missing-row model recently proposed [Zeng et al., Surf. Sci. 208, L7 (1989)] is extended to include a 0.30-Å lateral relaxation for top-layer copper atoms adjacent to the missing rows, and small (around 0.10-Å) vertical relaxations in both the first and second copper layers. These features yield the best correspondence between experimental and calculated LEED intensities yet reached for this surface structure.

• Received 2 July 1990

DOI:https://doi.org/10.1103/PhysRevB.42.11926