AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS2-MoA

Paper SS2-MoA7
Chemical Diffusion, Percolation, and Order-Disorder Transitions in a Model for CO-Oxidation with c(2x2)-O Ordering

Monday, October 25, 1999, 4:00 pm, Room 607

Session: Reactions on Metals
Presenter: D.-J. Liu, Iowa State University
Authors: D.-J. Liu, Iowa State University
E.W. James, Iowa State University
J.W. Evans, Iowa State University
Correspondent: Click to Email
Pattern formation during CO-oxidation on single crystal surfaces is mediated by the chemical diffusion of adsorbed CO in a disordered environment of coadsorbed relatively immobile oxygen. We analyze CO-diffusion in a lattice-gas models for this reaction which incorporates c(2x2) ordering of adsorbed oxygen,@footnote 1@ and thus preferential diffusion at higher oxygen coverages of CO along anti-phase boundaries between c(2x2)-O domains. This constitutes a novel type of problem involving transport in a disordered medium, where CO-diffusion is blocked by percolation of the c(2x2)-O domains. We further show that such percolation is strongly influenced by (but not necessarily coincident with) a c(2x2) order-disorder transition in the oxygen overlayer. The latter constitutes a non-equilibrium analogue of order-disorder transitions familiar in equilibrated adlayers with short-range repulsive interactions. Precise results characterizing diffusion, percolation, and the order-disorder transition are obtained from extensive Monte Carlo simulations. @FootnoteText@ @footnote 1@ Y. Suchorski, J. Beben, E.W. James, J.W. Evans, and R. Imbihl, Phys. Rev. Lett. 82 (1999) 1907.