On the phase separation of a binary fluid in a porous medium

¹ Institut für Theoretische Physik and Center for Computational Materials Science TU Wien - Wiedner Hauptstraße 8-10, A-1040 Wien, Austria
² Laboratoire de Physique Théorique, UMR 8627, Bât. 210, Université de Paris-Sud F-91405 Orsay Cedex, France

Received: 15 January 2001
Accepted: 10 May 2001

Abstract

Our investigations of the phase diagram of a symmetric binary fluid in equilibrium with a porous matrix show that moderate changes in the properties of the matrix or in the matrix-fluid interaction lead to drastic modifications of the phase diagram of the fluid. Thus our results confirm on a qualitative basis recent experimental data. The phase diagrams that we have obtained show a wide variation and can be classified in terms of archetypes of systems of two order parameters. These different types can be characterised in terms of the loci where the λ-line of the demixing transition intersects the first-order liquid-vapour coexistence curve. Results are based on the optimised random phase approximation and on grand-canonical Monte Carlo simulations.