Structure determination of Ag(111)(root 3X root 3)R30 degrees-Sb by low-energy electron diffraction

A quantitative structure determination of the Ag(111)(root 3 x root 3)R30 degrees-Sb surface has been performed using low energy electron diffraction. Six possible structural models were tested: Sb overlayers with four different adsorption sites and a substitutional alloy surface layer, with or without a stacking fault relative to the underlying substrate. The results clearly favor the faulted alloy surface model with all outermost layer Sb and Ag atoms occupying hcp hollow sites, in agreement with a recent x-ray diffraction study of this surface phase and both x-ray diffraction and medium energy ion scattering studies of the related Cu(111)(root 3 x root 3)R30 degrees-Sb surface