Thermodynamic perturbation theory for a valence-limited model of colloidal systems

Abstract

Thermodynamic perturbation theory for central force associating potential is extended and applied to describe the properties of the valence-limited model of colloidal fluids. The model, which has been developed by Speedy and Debenedetti in early 1990s (R. J. Speedy, P. G. Debenedetti, Mol. Phys. 81, 237(1994)), is represented by the fluid of non-additive square-well hard spheres with a predefined maximum number of bonds that each particle can form. The theory takes into account ring formation and higher order distribution functions of the reference system. To assess the accuracy of the theory, we perform extensive Monte Carlo simulations for the original version of the model and its limiting version with square-well potential represented by the sticky Baxter interaction. Theoretical predictions for thermodynamic properties (pressure, energy, entropy) and fractions of n-time bonded particles are in good agreement with corresponding computer simulation predictions. Results of the theory for the liquid–gas phase diagram of the model with are less accurate.