Low-density crystals in charged colloids : Comparison with Yukawa theory

TL;DR

This study investigates low-density charged colloid crystals with long-range interactions, comparing experimental results to Yukawa theory, revealing both agreement in freezing points and unexpected crystal structures.

Contribution

It provides the first detailed comparison between experimental colloid crystals at low density and Yukawa theoretical predictions, highlighting discrepancies in crystal polymorphs.

Findings

Freezing point matches Yukawa theory predictions.

Observation of body-centred cubic crystals instead of face-centred cubic.

Long Debye screening length influences crystal structure formation.

Abstract

Charged colloids can behave as Yukawa systems, with similar phase behaviour. Using particle- resolved studies, we consider a system with an unusually long Debye screening length which forms crystals at low colloid volume fraction {\phi} ~ 0.01. We quantitatively compare this system with the Yukawa model and find that its freezing point is compatible with the theoretical prediction but that the crystal polymorph is not always that expected. In particular we find body-centred cubic crystals where face-centred cubic crystals are expected.