Gas Model and Elementary Processes

The simplest model of the condensed phase is represented by the lattice-gas model [50]. It reflects two major features of the any species in the condensed phase, viz., their characteristic volume and species interactions. The volume of a crystalline solid is characterized by its natural lattice. With a good approximation, one can consider that the subsurface region of a solid is 

at any site there must be a particle of one species or another Y i= ff — First, let us consider the ideal models that take into account a characteristic volume of the adspecies only, and the ideas of the lateral interactions between the adspecies. 

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