Surface x-ray diffraction study of the Rh(100)(2x2)-O reconstruction

The 0.5 ML oxygen-induced reconstruction of the Rh(100) surface has been in vestigated using surface x-ray diffraction. The rhodium atoms in the surfac e layer adopt a "clock'' reconstruction with an in-plane displacement of th e surface-layer Rh atoms of d(Rhxy) = 0.19 +/- 0.02 Angstrom. The oxygen at oms were found to be situated in the "diamond" site rather than the rotated fourfold hollow site, with an in-plane displacement of 0.20 +/- 0.05 Angst rom on either side of the center. This work supports the conclusions of rec ent density-functional theory and low-energy-electron-diffraction work.