Full-coverage adsorption structure of H/Rh(110)

Abstract

At full coverage, adsorption of hydrogen on Rh(110) develops a 1*1-2H structure. A LEED structure analysis-though restricted to integer-order beam spectra only-is able to detect the adsorption position, which is 0.78 AA above the first substrate layer occupying nearly but not exactly threefold-coordinated sites at a lateral distance of 0.98 AA from the Rh rows. So, nearly equidistant hydrogen rows are observed. However, because of missing superstructure spots and a weak influence of hydrogen on integer-order spot intensities, comparatively large error bars of up to +or-0.3 AA result for hydrogen structure parameters. Nevertheless the minimum Pendry R-factor is as low as 0.28. Hydrogen removes the multi-layer relaxation observed for the clean surface towards bulk distances with only a 1.6% contraction between the first and second layer. This is in agreement with previous calculations neglecting hydrogen at the price of a less confident R-factor (0.37).