Freezing of Charge-Stabilized Colloidal Dispersions

Abstract

The Rogers−Young approximation for the Ornstein−Zernike integral equation is combined with the Hansen−Verlet one-phase criterion for freezing to predict freezing of a hard core repulsive Yukawa model (HCRYM) fluid. Comparison of theoretical predictions with corresponding computer simulation data discloses the superiority of the Rogers−Young approximation over the hypernetted chain approximation and the rescaled mean spherical approximation for freezing. Then, the Rogers−Young approximation combined with the Hansen−Verlet one-phase criterion is employed for the freezing of many-component charge-stabilized colloidal dispersions, which consist of colloidal macroions, electrolyte small ions, and solvent molecules and are modeled as a single-component charged hard core macroion interacting through a screened Coulomb potential. The theoretically predicted freezing line with the macroion surface charge number being assumed as an adjustable parameter is in very good agreement with the corresponding experimental data. The reason why, by the empirical Hansen−Verlet structure function approach, the single-component coarse-grained effective potential is valid for the freezing description of the many-component charge-stabilized colloidal solutions but not valid for the case of asymmetric binary hard sphere mixtures is discussed.