  It is found experimentally that the coexistence region of a vapor-liquid
system or a binary mixture is substantially narrowed when the fluid is confined
in a aerogel with a high degree of porosity (e.g. of the order of 95% to 99%).
A Hamiltonian model for this system has recently been introduced (J.Donley PRE
55:539, 1997}. We have performed Monte-Carlo simulations for this model to
obtain the phase diagram for the model. We use a periodic fractal structure
constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to
simulate a realistic gel environment. The phase diagram obtained is
qualitatively similar to that observed experimentally. We also have observed
some metastable branches in the phase diagram which have not been seen in
experiments yet. These branches, however, might be important in the context of
recent theoretical predictions and other simulations.
