Phase separation of binary liquid mixtures of hard spheres and Yukawa particles

By solving the Ornstein-Zernike equation together with the Rogers-Young closure relation for the correlation functions of binary liquid mixtures of hard spheres and Yukawa particles we calculate the concentration-concentration structure factor, S-cc(k), for different values of the diameter ratio and molar fraction of the mixtures. For hard spheres much larger than the Yukawa particles, and for large values of the molar fraction of the latter, we find a divergence of the value of S-cc(k) at k = 0, which signals the limit of thermodynamic stability with respect to phase separation. At the same time, from the form of the partial radial distribution functions of systems near to the instability we conclude that the phase separated systems are composed of one phase rich in hard spheres, whose structure may be interpreted in terms of bridge formation, immersed in an other rich in Yukawa particles.