AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA9
NIXSW Analysis of the Disorder Transition of Chlorine on Cu(111)

Wednesday, November 6, 2002, 4:40 pm, Room C-110

Session: Structure and Chemistry at Metal Surfaces
Presenter: A.G. Shard, University of Sheffield, UK
Authors: A.G. Shard, University of Sheffield, UK
C. Ton-That, University of Cambridge, UK
P.A. Campbell, University of Dundee, UK
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Chlorine adsorbs on Cu(111) primarily in threefold hollow sites, with a slight preference for the 'fcc' site (above a third layer copper atom) as opposed to the 'hcp' site. We have monitored the relative population of the two sites at a variety of coverages and temperatures using Normal Incidence X-ray Standing Waves (NIXSW). Disordered surfaces at low coverages or high temperatures have approximately equal populations of the two hollow sites, providing a measure of confirmation for the small energy difference recently calculated between them.@footnote 1@ Adsorption of chlorine to a Cu(111) crystal at 180K results in an ordered root 3 surface, with equal populations of 'fcc' and 'hcp' sites, implying the prolonged existence of metastable 'hcp' domains at this temperature. The room temperature root 3 structure has a large 'fcc' population, which decreases close to the disorder transition at 350K. These data are discussed and compared with Monte Carlo simulations. @FootnoteText@ @footnote 1@K. Doll and N. M. Harrison, Chem. Phys. Lett., 317, 282 (2000).