EXTENDED MEAN FIELD APPROACH TO ANALYZING PATTERN FORMATION IN SURFACE CHEMICAL REACTIONS

E. E. Mola (), D. A. King, I. M. Irurzun, M. Rafti and J. L. Vicente
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E. E. Mola: INIFTA, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (UNLP, CONICET, CICPBA), Suc. 4, Casilla de Correo 16 (1900) La Plata, Argentina
D. A. King: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 IEW, UK
I. M. Irurzun: INIFTA, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (UNLP, CONICET, CICPBA), Suc. 4, Casilla de Correo 16 (1900) La Plata, Argentina
M. Rafti: INIFTA, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (UNLP, CONICET, CICPBA), Suc. 4, Casilla de Correo 16 (1900) La Plata, Argentina
J. L. Vicente: INIFTA, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (UNLP, CONICET, CICPBA), Suc. 4, Casilla de Correo 16 (1900) La Plata, Argentina

Surface Review and Letters (SRL), 2004, vol. 11, issue 01, 57-70

Abstract: In this paper we apply a model of surface chemical reactions to describe pattern formation in theCOoxidation on Pt(100). The model is an extended mean field approximation (EMFA), where two coupling processes are included: gas global coupling (to take into account the mass chemical reaction balance) andCOdiffusion. The surface is divided intoM×Mcells; inside each of them the mean field approximation (MFA) is fulfilled. Anisotropic diffusion between nearest neighbor cells and gas coupling among all cells are also allowed.The EMFA goes beyond the traditional reaction–diffusion approaches with Fickian terms, in favor of a more general mass balance equation that consistently incorporates the coupling betweenCOdiffusion and the nonlinear phase transition of the substrate.In this paper we study three different cases: (a) homogeneous coverage oscillations — whenCOandO2partial pressures are kept constant and the whole set ofM×Mcells have the same value of partial coverages and phase fractions; in this case the system exhibits self-oscillations, such as those experimentally observed; (b) inhomogeneous coverage oscillations — whenCOandO2partial pressures are kept constant and inhomogeneities of coverage are present; the system evolves byCOdiffusion between nearest neighbor cells; (c) gas global coupling — when gas global coupling is allowed and inhomogeneities of coverage are present, there are oscillations in the gas phase that follow the surface evolution.

Keywords: Models of surface chemical reactions; platinum; carbon monoxide; single crystal surfaces; surface defects; solid–gas interfaces; adatoms; 82.20.Wt; 47.54.+r; 82.20.Mj; 82.65.Jv (search for similar items in EconPapers)
Date: 2004
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DOI: 10.1142/S0218625X04005883

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