Thermodynamic properties of a system of interacting particles adsorbed on a lattice with two nonequivalent sites - art. no. 165423

We investigate the thermodynamic properties of a system of particles adsorb ed on a lattice with two nonequivalent sites, with different unit cell numb ers and adsorption energies. We include lateral interactions between partic les in the nearest-neighbor nonequivalent sites. We use the decoration-iter ation transformation in order to reduce the problem to the Ising spin squar e ferromagnet in a magnetic field. The phase diagram of the system for the case of repulsive interaction differs considerably from the phase diagram o f an ordinary lattice gas with equivalent sites and shows nonmonotonic depe ndence of the critical temperature T-c on adparticle surface coverage theta . Using the real-space renormalization group method we also calculate adsor ption isotherms and coverage dependencies of the isothermal susceptibility for attractive and repulsive interactions. These functions exhibit features characteristic for systems with simultaneous repulsive and attractive inte ractions. Results from Monte Carlo simulations are in good agreement with t heory.