Reentrant crystallization of like-charged colloidal particles in an electrolyte solution: Relationship between the shape of the phase diagram and the effective potential of colloidal particles

The reentrant crystallization of like-charged colloidal particles in electrolyte solutions was studied to clarify the relationship between the shape of the phase diagram and the particle-particle effective potential. Coexisting densities were calculated at various electrolyte concentrations using the thermodynamic perturbation expansion method with effective one-component models. The effective potentials were obtained using an integral equation theory for liquids. Some model effective potentials were examined. The calculated results indicated that the reentrant behaviors of various acidic protein solutions observed in the experiments required not only the nonmonotonic dependence of the short-range attraction on the electrolyte concentration, but also the absence of a long repulsive tail.