Computer simulations of phase equilibrium for a fluid confined in a disordered porous structure

We present calculations of the phase diagrams of a Lennard-Jones 12-6 fluid confined in a disordered porous structure made up of a dispersion of spher ical particles, following up on an earlier work on the same system. In part icular we present additional calculations using more realizations of the ma trix and we investigate the applicability of the Gibbs-Duhem integration me thod to the calculation of phase equilibrium in these systems. The essentia l picture of disordered and inhomogeneous coexisting vapor and liquid phase s, which emerged in the earlier work, is confirmed by the new calculations. However, a second phase transition associated with the wetting of the poro us material by the fluid is found to be more sensitive to variations of the matrix realization. While for the present model this transition appears fo r particular realizations of the matrix, it does not seem to survive averag ing over realizations.