The adsorption geometry of Ag(1 1 1)–(√7×√7)R19.1°-4Ar studied by LEED

The adsorption geometry of Ag(1 1 1)–(√7×√7)R19.1°-4Ar was studied using low-energy electron diffraction (LEED). This higher-order commensurate phase was produced by preadsorbing a small amount of CO in order to block the close-packed steps, which pin the rotation angle of the overlayer. The dynamical LEED data were taken at a sample temperature of 31 K, and the results of the LEED analysis indicate that one Ar atom per unit cell occupies the top of a Ag substrate atom, while the other three Ar atoms occupy bridge sites. There is little, if any, distortion of the Ar lattice from hexagonal symmetry. The average Ar–Ag perpendicular spacing in this structure is 3.22±0.07 Å. The Ar–Ag nearest-neighbor distances are 3.22 and 3.52 Å for top-site and bridge-site Ar atoms, respectively.