  The statistical thermodynamics of polyatomic species mixtures adsorbed on
two-dimensional substrates was developed on a generalization in the spirit of
the lattice-gas model and the classical Guggenheim-DiMarzio approximation. In
this scheme, the coverage and temperature dependence of the Helmholtz free
energy and chemical potential are given. The formalism leads to the exact
statistical thermodynamics of binary mixtures adsorbed in one dimension,
provides a close approximation for two-dimensional systems accounting multisite
occupancy and allows to discuss the dimensionality and lattice structure
effects on the known phenomenon of adsorption preference reversal.
