Crystalline phases of polydisperse spheres

TL;DR

This study uses advanced simulation and theoretical methods to show that dense polydisperse spheres at equilibrium tend to separate into multiple fractionated fcc phases, with the number of phases increasing with size distribution spread.

Contribution

It provides conclusive evidence of phase demixing in polydisperse spheres and tracks up to four coexisting phases, revealing nearly continuous demixing transitions and size fractionation.

Findings

Polydisperse spheres demix into multiple fcc phases.

Number of phases increases with size distribution spread.

Demixing transitions can be nearly continuous.

Abstract

We use specialized Monte Carlo simulation methods and moment free energy calculations to provide conclusive evidence that dense polydisperse spheres at equilibrium demix into coexisting fcc phases, with more phases appearing as the spread of diameters increases. We manage to track up to four coexisting phases. Each of these is fractionated: it contains a narrower distribution of particle sizes than is present in the system overall. We also demonstrate that, surprisingly, demixing transitions can be nearly continuous, accompanied by fluctuations in local particle size correlated over many lattice spacings.