A PERTURBATION TREATMENT OF THE ORDER-DISORDER PHASE-TRANSITION IN COLLOIDAL SUSPENSIONS

The hard sphere perturbation model developed by H. S. Kang et al. (J. Chem. Phys. 82, 414 (1985)) is applied to particles interacting with screened coulomb pair potentials. The success of the model at predicting the coexistence parameters of the phase transition from a liquid to a face-centered cubic solid observed in colloidal suspensions is due to the use in the model of a volume fraction-dependent reference hard sphere diameter. Comparison is made between model predictions and machine calculations showing excellent agreement under conditions where the pair interactions are very soft (i.e., low ionic strength and high surface potentials). In addition, model predictions are compared with phase transition data that have been reported on a variety of latex suspensions. The results suggest that the model captures the physical properties of the phase transition in colloidal suspensions quite well and that failures can be attributed to a poor understanding of the chemistry giving rise to particle charge and how this charge varies with the particle's local electrolyte environment. © 1991.