Global phase diagram for monomer/dimer mixtures

The basic features of the global phase diagram associated with the generalized Flory dimer (GFD) equation of state for mixtures of square-well monomers and dimers are calculated. We first extend the GFD theory to square-well monomer/chain mixtures. Theoretical predictions for the compressibility factor as a function of volume fraction are in good agreement with discontinuous molecular dynamics simulation results for monomeddimer and monomers/8-mer mixtures. The GFD-predicted global phase diagram for square-well monomer/dimer mixtures is estimated using a brute force method. The locus of critical points in the P-T plane is calculated over a grid of points in the Lambda-zeta plane, where zeta is a measure of the difference between the monomer and dimer well depths and A is a measure of the strength of the attraction between monomers and dimers. The major topographical features of our global phase diagram are similar to those predicted for other equations of state. (C) 2002 Elsevier Science B.V. All rights reserved.