Title
CO-oxidation model with superlattice ordering of adsorbed oxygen. I. Steady-state bifurcations
Campus Units
Mathematics, Ames Laboratory
Document Type
Article
Publication Date
10-1999
Journal or Book Title
Journal of Chemical Physics
Volume
111
Issue
14
First Page
6579
Last Page
6589
DOI
10.1063/1.479949
Abstract
We analyze a model for CO oxidation on surfaces which incorporates both rapid diffusion of adsorbed CO, and superlattice ordering of adsorbed immobile oxygen on a square lattice of adsorption sites. The superlattice ordering derives from an “eight-site adsorption rule,” wherein diatomic oxygen adsorbs dissociatively on diagonally adjacent empty sites, provided that none of the six additional neighboring sites are occupied by oxygen. A “hybrid” formalism is applied to implement the model. Highly mobile adsorbed CO is assumed randomly distributed on sites not occupied by oxygen (which is justified if one neglects CO–CO and CO–O adspecies interactions), and is thus treated within a mean-field framework. In contrast, the distribution of immobile adsorbed oxygen is treated within a lattice–gas framework. Exact master equations are presented for the model, together with some exact relationships for the coverages and reaction rate. A precise description of steady-state bifurcation behavior is provided utilizing both conventional and “constant-coverage ensemble” Monte Carlo simulations. This behavior is compared with predictions of a suitable analytic pair approximation derived from the master equations. The model exhibits the expected bistability, i.e., coexistence of highly reactive and relatively inactive states, which disappears at a cusp bifurcation. In addition, we show that the oxygen superlattice ordering produces a symmetry-breaking transition, and associated coarsening phenomena, not present in conventional Ziff–Gulari–Barshad-type reaction models.
Rights
Copyright 1999 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Copyright Owner
American Institute of Physics
Copyright Date
1999
Language
en
File Format
application/pdf
Recommended Citation
James, E. W.; Song, C.; and Evans, James W., "CO-oxidation model with superlattice ordering of adsorbed oxygen. I. Steady-state bifurcations" (1999). Mathematics Publications. 29.
https://lib.dr.iastate.edu/math_pubs/29
Comments
The following article appeared in Journal of Chemical Physics 111, 14 (1999): 6579 and may be found at doi:10.1063/1.479949.