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Kinetic phase transitions in a model for surface catalysis
A513 409
Surface Science 221 (1989) 409-426 North-Holland, Amsterdam KINETIC PHASE TRANSITIONS FOR SURFACE P. F I S C H E R
IN A MODEL
CATALYSIS
and U.M. TITULAER
Institut ]'fir Theoretlsche Physik, Johannes Kepler Unwerstt~it Linz, A-4040 Ltnz, Austrta Received g March 1989; accepted for publication 18 May 1989 We consider a kinetic model, recently proposed by Ziff, Gulari, and Barshad, that reproduces some features of the surface-catalyzed oxidation of CO; in particular the model shows transitions between poisoned and active states of the catalytic surface. The behavior of the model in mean field theory was studied by Dickman. It becomes analogous to that of known models for equihbrium and non-equihbrium phase transitions when non-reactive desorption of reactants is allowed; this also eliminates spurious stationary states. It then becomes possible to determine the relative stability of the two remaining stable stationary states, and hence to locate the phase transition, by studying an interface between the two phase.s, usin8 a version of mean field theory for irthomogeneous systems. This new method for locating the phase transition in the context of a mean field treatment is the main new result of our paper. The adequacy of mean field theory can be estimated by comparison with a treatment of Bethe-Peierls type, a variant of mean field theory in which nearest neighbor correlations are taken into account. Mean field treatments seem particularly suitable for obtaining a quick impression of the consequences of changes in the model dlesigned to include f ~ effeL-'Lsknown to be important in real catalysts.
Surface Science 221 (1989) 409-426 North-Holland, Amsterdam KINETIC PHASE TRANSITIONS FOR SURFACE P. F I S C H E R
IN A MODEL
CATALYSIS
and U.M. TITULAER
Institut ]'fir Theoretlsche Physik, Johannes Kepler Unwerstt~it Linz, A-4040 Ltnz, Austrta Received g March 1989; accepted for publication 18 May 1989 We consider a kinetic model, recently proposed by Ziff, Gulari, and Barshad, that reproduces some features of the surface-catalyzed oxidation of CO; in particular the model shows transitions between poisoned and active states of the catalytic surface. The behavior of the model in mean field theory was studied by Dickman. It becomes analogous to that of known models for equihbrium and non-equihbrium phase transitions when non-reactive desorption of reactants is allowed; this also eliminates spurious stationary states. It then becomes possible to determine the relative stability of the two remaining stable stationary states, and hence to locate the phase transition, by studying an interface between the two phase.s, usin8 a version of mean field theory for irthomogeneous systems. This new method for locating the phase transition in the context of a mean field treatment is the main new result of our paper. The adequacy of mean field theory can be estimated by comparison with a treatment of Bethe-Peierls type, a variant of mean field theory in which nearest neighbor correlations are taken into account. Mean field treatments seem particularly suitable for obtaining a quick impression of the consequences of changes in the model dlesigned to include f ~ effeL-'Lsknown to be important in real catalysts.