Abstract
We simulate a strongly size-disperse hard-sphere fluid confined between two parallel, hard walls. We find that confinement induces crystallization into n-layered hexagonal lattices and a novel honeycomb-shaped structure, facilitated by fractionation. The onset of freezing prevents the formation of a stable glass phase and occurs at much smaller packing fraction than in bulk. Varying the wall separation triggers solid-to-solid transitions and a systematic change of the size-distribution of crystalline particles, which we rationalize using a semi-quantitative theory. We show that the crystallization can be exploited in a wedge geometry to demix particles of different sizes.
Highlights
Confinement occurs naturally in many physical, chemical, and biological systems, such as nanotubes, porous rocks, or crowded living cells
Even for the simplest case of monodisperse hard spheres confined between parallel hard walls one observes spatially inhomogeneous density profiles and diffusivities [1,2], anisotropic structure factors [3,4], multiplereentrant glass transitions [5,6] and solid-to-solid transitions between different crystalline phases [7,8,9,10]
We have studied the crystallization of size-disperse hard spheres in a confined geometry
Summary
Confinement occurs naturally in many physical, chemical, and biological systems, such as nanotubes, porous rocks, or crowded living cells. For the study of structural relaxation in supercooled liquids and glasses a size dispersity must be introduced to prevent crystallization even at very small packing fractions [6,12,13] Despite their popularity as model glass formers, recent observations in bulk have revealed that Gaussiandistributed hard spheres [37,38,39,40] as well as the often used Kob-Anderson model [41,42] form crystals already in the supercooled regime. This crystallization is induced by a process called fractionation which describes the separation of a homogeneous fluid into different liquid or crystalline fractions with very different particle-size distributions.
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