Entropy driven demixing in mixtures of hard convex bodies

Abstract

Fluid–fluid phase separation in binary mixtures of hard convex particles can arise with substantial asymmetry between the breadth of the molecular species, at least one of which must be non-spherical. This result is obtained by using a geometrical approximation for the Ornstein–Zernicke direct correlation function within a density functional theory consistent with the free energy of the Scaled Particle approximation. When both fluids are rigidly ordered, the present theory indicates that fluid–fluid demixing occurs through loop spinodals. When applied for the case of strictly two-dimensional fluid, the theory predicts that the mixture is always stable.