Adsorption thermodynamics with multisite occupancy at criticality

The thermodynamics of interacting homonuclear dimers adsorbed on homogeneou s surfaces in-a monolayer regime is addressed. Dimer adsorption is describe d in the framework of the lattice gas theory. Hypercubic lattices are used as a model of homogeneous substrate in one and two dimensions. The effect o f lateral interactions on the behavior of the adlayer is considered. The ad sorption isotherm, energy of adsorption, differential heat of adsorption, a nd configurational entropy are obtained by Monte Carlo simulations and comp ared with analytical calculations. Particular attention is devoted to the t wo-dimensional case with repulsive nearest neighbor lateral interactions in the critical and subcritical regime. Different ordered phases are observed and their relationship with the behavior of the thermodynamic functions of the adsorbed monolayer is shown.