ADSORPTION SITE CHANGE FOR <font>Cs</font>, <font>Rb</font> OR <font>K</font> ADSORPTION ON <font>Ag</font>(111)

Abstract

The adsorption geometries for the primitive (3×3), (2×2) and ([Formula: see text] structures of K, Rb and Cs on Ag(111) have been determined using low-energy electron diffraction. In the lower-coverage (3×3) and (2×2) structures, the adatoms occupy fcc hollow sites, while in the [Formula: see text]; structure they occupy the hcp hollow sites. The fcc hollow structures are accompanied by significant substrate rumpling. There is no significant coverage-dependent or site-dependent change in chemisorption bond length. However, there is a large coverage-dependent anisotropy of vibrational amplitude of the adatoms, with the parallel component as much as five times larger than the perpendicular component at low coverages.