Complex fluid behavior of strongly asymmetric binary mixtures. Thermodynamic properties of a generalized Lin-Taylor model

A detailed analysis is made of the lattice model of binary mixtures A± B, proposed a few years ago by Lin and Taylor. This model exhibits ̄ uid± ̄ uid immiscibility and a closed loop of immiscibility. Based on general arguments, the distinct possible behaviour is examined as a function of the coupling parameters, temperature and pressure in di erent lattices. The phase diagram is found to be richer than that reported previously, even in the square lattice case. The system, for attractive A± A interactions, shows the disappearance of one of the critical points for pressures lower than the A-pure system critical pressure. On the other hand, the mixture displays closed-loop behaviour without a low temperature immiscibility region for values of the interaction parameters e AA < 0 and e AB < e AA /2