Rescaled density expansions and demixing in hard-sphere binary mixtures

Abstract

The demixing transition of a binary fluid mixture of additive hard spheres is analyzed for different size asymmetries by starting from the exact low-density expansion of the pressure. Already within the second virial approximation the fluid separates into two phases of different composition with a lower consolute critical point. By successively incorporating the third, fourth, and fifth virial coefficients, the critical consolute point moves to higher values of the pressure and to lower values of the partial number fraction of the large spheres. When the exact low-density expansion of the pressure is rescaled to higher densities as in the Percus-Yevick theory, by adding more exact virial coefficients a different qualitative movement of the critical consolute point in the phase diagram is found. It is argued that the Percus-Yevick factor appearing in many empirical equations of state for the mixture has a deep influence on the location of the critical consolute point, so that the resulting phase diagram for a prescribed equation has to be taken with caution.

5 pages, 1 figure; to be published in The Journal of Chemical Physics

References in corpus (2)

• Contact values of the radial distribution functions of additive hard-sphere mixtures in d dimensions: A new proposal
• Demixing in binary mixtures of hard hyperspheres

Cited by in corpus (5)

• Structural and Thermodynamic Properties of Hard-Sphere Fluids
• Alternative Approaches to the Equilibrium Properties of Hard-Sphere Liquids
• Demixing can occur in binary hard-sphere mixtures with negative non-additivity
• Virial coefficients and demixing in the Asakura-Oosawa model
• Communication: Virial coefficients and demixing in highly asymmetric binary additive hard-sphere mixtures