Effect of many-body interactions on the solid-liquid phase-behavior of charge-stabilized colloidal suspensions

TL;DR

This study investigates how many-body interactions influence the solid-liquid phase behavior of charge-stabilized colloids, revealing deviations from Yukawa pair-potential predictions at low ionic strength and proposing an improved density-dependent potential.

Contribution

It introduces a combined Poisson-Boltzmann and molecular dynamics approach to include many-body effects and proposes a modified Yukawa potential for better phase behavior prediction.

Findings

Good agreement with Yukawa theory at high salt conditions

Deviations at low ionic strength due to many-body interactions

Proposed a density-dependent truncated Yukawa potential

Abstract

The solid-liquid phase-diagram of charge-stabilized colloidal suspensions is calculated using a technique that combines a continuous Poisson-Boltzmann description for the microscopic electrolyte ions with a molecular-dynamics simulation for the macroionic colloidal spheres. While correlations between the microions are neglected in this approach, many-body interactions between the colloids are fully included. The solid-liquid transition is determined at a high colloid volume fraction where many-body interactions are expected to be strong. With a view to the Derjaguin-Landau-Verwey-Overbeek theory predicting that colloids interact via Yukawa pair-potentials, we compare our results with the phase diagram of a simple Yukawa liquid. Good agreement is found at high salt conditions, while at low ionic strength considerable deviations are observed. By calculating effective colloid-colloid pair-interactions it is demonstrated that these differences are due to many-body interactions. We suggest a density-dependent pair-potential in the form of a truncated Yukawa potential, and show that it offers a considerably improved description of the solid-liquid phase-behavior of concentrated colloidal suspensions.