Crystal Nucleation of Highly-Screened Charged Colloids

TL;DR

This study investigates how slight charges on colloidal particles influence their phase behavior and nucleation, revealing that even minimal charge significantly alters nucleation barriers and phase boundaries.

Contribution

The paper introduces a detailed simulation approach to quantify the impact of small charges on colloid phase diagrams and nucleation, highlighting the importance of Debye screening length.

Findings

Small charges significantly affect phase boundaries.

Nucleation barriers depend on Debye screening length.

Even minimal charge causes marked differences from hard spheres.

Abstract

We study the nucleation of nearly-hard charged colloidal particles. We use Monte Carlo simulations in combination with free-energy calculations to accurately predict the phase diagrams of these particles and map them via the freezing density to hard spheres, then we use umbrella sampling to explore the nucleation process. Surprisingly, we find that even very small amounts of charge can have a significant effect on the phase behavior. Specifically, we find that phase boundaries and nucleation barriers are mostly dependent on the Debye screening length, and that even screening lengths as small as 2% of the particle diameter are sufficient to show marked differences in both. This work demonstrates clearly that even mildly charged colloids are not effectively hard spheres.