The definition of a standard model

Several simulation models have been introduced in the past for surface reactions, including energetic interactions [16, 35-37]. These models are very difficult to compare to each other because they use very different descriptions of the individual reaction steps. Furthermore, steps which are considered to be independent of energetic interactions in one paper, show a dependency in another paper. Therefore it is necessary and useful to introduce a kind of the standard model [38] in order to compare different models in the future. 

First of all, we define the transition rates for our stochastic model using an ansatz of Kawasaki [39, 40]. In the following we use the abbreviation X for an initial state ai for mono- and cr cr for bimolecular steps), F for a final state cr[ for mono- and cr cr for bimolecular steps) and Z for the states of the neighbourhood for mono- and for 

For this (reversible) process we write down the following Markovian master equation 

For the reversible processes we can define the ratio of the transition rates using equation (9.2.30)  

In order to define the rates we need an additional condition. We use the symmetric condition (which constitutes the second condition of the standard model) 

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