Large effect of polydispersity on defect concentrations in colloidal crystals

TL;DR

This study reveals that polydispersity significantly impacts defect concentrations in colloidal crystals, notably increasing interstitial defects by up to six orders of magnitude due to the presence of small particles.

Contribution

It demonstrates how polydispersity affects defect types and concentrations in colloidal crystals, highlighting the role of small particles in defect formation.

Findings

Interstitial defect concentration can increase by six orders of magnitude with polydispersity.

Vacancy concentration decreases by about half in polydisperse crystals.

Stacking fault concentration remains similar to monodisperse crystals.

Abstract

We compute the equilibrium concentration of stacking faults and point defects in polydisperse hard-sphere crystals. We find that, while the concentration of stacking faults remains similar to that of monodisperse hard sphere crystals, the concentration of vacancies decreases by about a factor two. Most strikingly, the concentration of interstitials in the maximally polydisperse crystal may be some six orders of magnitude larger than in a monodisperse crystal. We show that this dramatic increase in interstitial concentration is due to the increased probability of finding small particles and that the small-particle tail of the particle size distribution is crucial for the interstitial concentration in a colloidal crystal.