SEXAFS studies above the O K-edge indicated that oxygen atoms were adsorbed in three-fold hollow sites close to the reconstructed and relaxed Cu(111) surface with a nearest-neighbour O-Cu bond length of 1.83Å. The Cu-Cu distance in the nearest-neighbour Cu shell on the surface was considerably larger than the Cu-Cu separation in bulk copper and close to the corresponding value for Cu2O. This reconstruction of the surface Cu layer on oxygen adsorption necessarily implies a marked surface relaxation.

Reconstruction and Relaxation of the Oxygen-Covered Cu(111) Surface - a SEXAFS Study. J.Haase, H.J.Kuhr: Surface Science, 1988, 203[3], L695-9