MEAN-SPHERICAL APPROXIMATION FOR A LATTICE MODEL OF A FLUID IN A DISORDERED MATRIX

We study a quenched-annealed lattice gas model of a fluid in a disorde red porous material. The formalism of liquid state statistical mechani cs is applied together with the replica method to investigate the phas e diagram of the system. In addition to mean-field predictions, exact solutions of the mean-spherical approximation (MSA) are provided for t he structural and thermodynamic properties in all dimensions. The MSA phase diagrams are in qualitative agreement with the liquid-gas coexis tence curves observed experimentally in porous media. An additional 'p re-condensation' transition may appear for a narrow range of the matri x-fluid parameters.