Adsorption geometry of Cu(1 1 0)-(12 × 2)-14Xe

Low-energy electron diffraction was used to study the adsorption geometry of Xe on Cu(1 1 0). At low temperatures, a higher-order commensurate (12 × 2) structure can be formed that consists of rows of Xe atoms aligned along the direction of the rows on Cu(1 1 0), and having a spacing between the rows equal to the Cu row spacing. A dynamical LEED study of this structure at 20 K indicates that the rows of Xe atoms are localized on top of the Cu substrate rows. The lateral registry of the Xe rows along the Cu rows includes 2 Xe atoms per (12 × 2) unit cell in atop positions above Cu atoms, with the others in lower-symmetry sites. The average Xe–Cu interlayer spacing is 3.3 ± 0.1 Å and there is a small degree (0.1 Å) of vertical rumple in both the overlayer and the top substrate layer. The substrate surface with adsorbed Xe has essentially the same relaxation as the clean surface. The analysis of the adatom vibrations in this structure indicates that the isotropically-averaged rms vibration amplitude is 0.2 Å for Xe, while that of the top-layer Cu atoms is 0.04 Å.