Adhesive-hard-sphere approximation for the structure of square-well fluids: application to colloidal dispersions

Abstract

The accuracy of the adhesive-hard-sphere (AHS) model in representing structure factors of the short-range square-well potentials is examined by comparing theoretical predictions with Monte Carlo simulations for the square-well fluids over a range of conditions. We show that the analytical solution for the structure factors of the AHS model can be used to describe structure factors of the square-well potential adequately at low to moderate volume fractions (ϕ < 0·26) when the range of the square-well potential is less than 20% of the particle diameter and the magnitude of the contact potential is less than 3. At low values of the width of the square well (less than 5% of the particle diameter), the AHS model can be applied to even larger values of the contact potential and to higher volume fractions. We also show that the AHS model can be used to describe accurately structure factors of the non-ionic micro-emulsions and inverted micellar systems containing sodium bis 2-ethylhexyl-sulphosuccinate (aerosol-OT) surfactant dispersed in oil.