Analytical equations of state for double Yukawa and hard core double Yukawa fluids: application to simple and colloidal fluids

Analytic, explicit and non-empirical equations of state for the double Yukawa and hard core double Yukawa fluids are presented. They are based on a second-order inverse temperature expansion of the free energy within the mean spherical approximation. These equations of state yield good results for the pressure and internal energy when compared with exact mean spherical approximation calculations or Monte Carlo simulations performed on various double Yukawa fluids modelling either simple fluids or more complex systems such as sterically stabilized colloidal dispersions. Liquid–vapour phase diagrams for simple fluids and the coexistence lines between the dilute and concentrated phases of colloidal dispersions are also well predicted except around the critical points.