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 our predictions are outlined.
Highlights
Binary mixtures consisting of nonadhesive particles in thermal equilibrium can demix if their constituents differ in size [1,2,3,4,5,6,7,8]
Nonadhesive binary mixtures that are far from thermal equilibrium may demix even when the particles are of equal size
We investigate binary mixtures of two particle species which differ only with respect to their diffusion constants and interact by a shortranged repulsive force
Summary
Binary mixtures consisting of nonadhesive particles in thermal equilibrium can demix if their constituents differ in size [1,2,3,4,5,6,7,8]. 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. Our Brownian dynamics simulations show that for sufficiently large relative differences in the diffusion constants an initially random distribution of hot and cold particles spontaneously segregates into a solidlike phase of cold particles surrounded by a gaslike phase of mainly hot particles; see Figs.
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