Phase diagrams of colloidal spheres with a constant zeta-potential

TL;DR

This paper investigates the phase behavior of colloidal spheres with constant zeta-potential, revealing how colloid discharging influences phase stability and results in fluid-dominated phase diagrams.

Contribution

It introduces a method to map colloidal suspension phase diagrams onto Yukawa systems using renormalized charges, accounting for colloidal discharging effects.

Findings

Phase diagrams show fluid dominance due to colloidal discharging.

fcc and bcc phases are present but less stable at certain conditions.

Colloidal discharging affects effective interactions and phase boundaries.

Abstract

We study suspensions of colloidal spheres with a constant zeta-potential within Poisson-Boltzmann theory, quantifying the discharging of the spheres with increasing colloid density and decreasing salt concentration. We use the calculated renormalized charge of the colloids to determine their pairwise effective screened-Coulomb repulsions. Bulk phase diagrams in the colloid concentration-salt concentration representation follow, for various zeta-potentials, by a mapping onto published fits of phase boundaries of point-Yukawa systems. Although the resulting phase diagrams do feature face-centered cubic (fcc) and body-centered cubic (bcc) phases, they are dominated by the (re-entrant) fluid phase due to the colloidal discharging with increasing colloid concentration and decreasing salt concentration.