Phase diagram of random lattice gases in the annealed limit

An analysis of the random lattice gas in the annealed limit is presented. T he statistical mechanics of disordered lattice systems is briefly reviewed. For the case of the lattice gas with an arbitrary uniform interaction pote ntial and random short-range interactions the annealed limit is discussed i n detail. By identifying and extracting an entropy of mixing term, a correc t physical expression for the pressure is explicitly given. The one-dimensi onal lattice gas with uniform long-range interactions and random short-rang e interactions satisfying a bimodal annealed probability distribution is di scussed. The model is exactly solved and is shown to present interesting be havior in the presence of competition between interactions, such as the pre sence of three phase transitions with different critical temperatures and t he occurrence of triple and quadruple points. (C) 1999 American Institute o f Physics. [S0021-9606(99)50102-5].