Random anisotropy in lattice gas model

We consider a lattice-gas model with infinite-range interaction with site d ependent random anisotropy distributed with a Gaussian distribution. The ra ndom anisotropy lattice-gas analogous of the random field Ising model is so lved exactly using a replica theory. We show that, at finite temperature, t he introduction of disorder eliminates completely the phase transition, and destroy the equivalence between real gases and Ising magnets. Whereas at T = 0, the density of occupied sites has a step-like behavior as function of the random anisotropy. (C) 1999 Elsevier Science B.V.