Vapor-liquid coexistence of fluids with attractive patches: An application of Wertheim’s theory of association

We compare simulations and theoretical predictions based on Wertheim's thermodynamic perturbation theory (TPT) for spheres that interact through an isotropic square well interaction coupled to patchy attractions. Following a proposal of Foffi and Sciortino [J. Phys. Chem. B 111, 9702 (2007)], we show that, if we use the second virial coefficient as a scaling parameter, a generalized law of corresponding states holds not only for the critical point but also for the vapor-liquid coexistence curve of patchy hard sphere fluids with the same numbers of single-bonded patches. The predictions for patchy square well fluids from Wertheim's TPT are in good agreement with Monte Carlo simulation data, although no aspects of universality were found. Instead, we find a crossover from the behavior of isotropically short-ranged attractive fluids to that of patchy hard sphere fluids as the strength of patchy interaction increases.