Phase diagram of a system of particles adsorbed on a lattice with two non-equivalent sites: repulsive interaction

We investigated phase diagram of a system of particles adsorbed on a lattice with two non-equivalent sites, the number of which in the elementary cell and adsorption energy is different. The repulsive lateral interaction between particles in the nearest neighbour non-equivalent sites is considered. The existence of phase transition was found, depending on the parameters of the system (the difference in adsorption energies and interaction energy) and on surface geometry. The phase diagram for repulsive interaction differs considerably from the phase diagram of an ordinary lattice gas with equivalent sites and shows non-monotonic dependence of the critical temperature Tc on adparticle surface coverage θ.