An O induced structure on Rh(111) displaying a (2√3 × 2√3)R30° periodicity with an oxygen coverage of 0.67 has been studied by high resolution core level spectroscopy, scanning tunneling microscopy and density functional theory. Although O favors fcc hollow sites in all other known phases, it occupies both fcc and hcp sites in this structure, which can not be explained by pairwise adsorbate repulsion only. For both the (2√3 × 2√3)R30° and the (2x2)-3O structure, our study also shows that a simple density-of-states contrast can lead to oxygen adatoms appearing as protrusions in STM images.
Corresponding author: L. Köhler. Reprints also available from M. Schmid (schmid).
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