Local structure-mobility relationships of confined fluids reverse upon supercooling

Abstract

We examine the structural and dynamic properties of confined binary hard-sphere mixtures designed to mimic realizable colloidal thin films. Using computer simulations, governed by either Newtonian or overdamped Langevin dynamics, together with other techniques including a Fokker-Planck equation-based method, we measure the position-dependent and average diffusivities of particles along structurally isotropic and inhomogeneous dimensions of the fluids. At moderate packing fractions, local single-particle diffusivities normal to the direction of confinement are higher in regions of high total packing fraction; however, these trends are reversed as the film is supercooled at denser average packings. Auxiliary short-time measurements of particle displacements mirror data obtained for experimental supercooled colloidal systems. We find that average dynamics can be approximately predicted based on the distribution of available space for particle insertion across orders of magnitude in diffusivity regardless of the governing microscopic dynamics.

7 pages, 7 figures

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Cited by in corpus (6)

• Diverging time scale in the dimensional crossover for liquids in strong confinement
• Non-monotonic effect of confinement on the glass transition
• Local structure-mobility relationships of confined fluids reverse upon supercooling
• Mode-coupling theory of the glass transition for colloidal liquids in slit geometry
• Static properties of quasi-confined hard-sphere fluids
• Dynamic properties of quasi-confined colloidal hard-sphere liquids near the glass transition