The A B2 — 0 reaction with energetic interactions

Let us study now a stochastic model for the particular A + B2 — 0 reaction with energetic interactions between the particles. The system includes adsorption, desorption, reaction and diffusion steps which depend on energetic interactions. The temporal evolution of the system is described by master equations using the Markovian behaviour of the system. We study the system behaviour at different values for the energetic parameters and at varying diffusion and desorption rates. The location and the character of the phase transition points will be discussed in detail. 

In order to understand the details of surface reactions computer simulations are a powerful tool. For A - - 5 B2 0 reaction Ziff, Gulari and Barshad have done the Monte Carlo simulations (the ZGB-model) [2]. The model takes into account the following steps, described by equations (9.1.39) to (9.1.41). 

In order to develop a more realistic model, additional aspects have been taken into account. The CO desorption can be modeled by equation (9.1.43). The additional aspect of CO desorption leads to the disappearance of the CO-poisoned state [15] because at every value of Tco adsorbed CO molecules are able to leave the surface. Many other investigations under various conditions have been performed, like energetic interactions [16], the aspect of physisorption and reaction via the Eley-Rideal mechanism [17]. 

In the model of Section 9.1.2 we use a stochastic ansatz which describes the system by using master equations (under the assumption that the system is Markovian). This ansatz takes explicitly into account correlations in the particle distribution on the lattice. The results turn out to be in overall good agreement with the ZGB-model. 

In order to get a more realistic description of surface reactions energetic interactions must be taken into account. We introduced in Section 9.2.1 a general model which is able to handle systems which include mono- and bimolecular steps like adsorption, desorption, diffusion and reaction [38]. Here we apply this model to an extended version of the ZGB-model which incorporates particle diffusion and desorption [41]. 

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