Binary Mixtures of Particles with Different Diffusivities Demix

TL;DR

This paper investigates how differences in particle diffusivity alone can cause phase separation in binary mixtures of equal-sized particles, revealing an effective attraction that leads to clustering and demixing.

Contribution

It demonstrates that diffusivity differences alone can induce phase separation, highlighting a new mechanism distinct from size or shape effects.

Findings

Less diffusive particles form clusters due to effective attraction

Phase separation occurs above a critical system size

Experimental tests are proposed to validate the predictions

Abstract

The influence of size differences, shape, mass and persistent motion on phase separation in binary mixtures has been intensively studied. Here we focus on the exclusive role of diffusivity differences in binary mixtures of equal-sized particles. We find an effective attraction between the less diffusive particles, which are essentially caged in the surrounding species with the higher diffusion constant. This effect leads to phase separation for systems above a critical size: A single close-packed cluster made up of the less diffusive species emerges. Experiments for testing of our predictions are outlined.