How short-range attractions impact the structural order, self-diffusivity, and viscosity of a fluid

Abstract

We present molecular simulation data for viscosity, self-diffusivity, and the local structural ordering of (i) a hard-sphere fluid and (ii) a square-well fluid with short-range attractions. The latter fluid exhibits a region of dynamic anomalies in its phase diagram, where its mobility increases upon isochoric cooling, which is found to be a subset of a larger region of structural anomalies, in which its pair correlations strengthen upon isochoric heating. This "cascade of anomalies" qualitatively resembles that found in recent simulations of liquid water. The results for the hard-sphere and square-well systems also show that the breakdown of the Stokes-Einstein relation upon supercooling occurs for conditions where viscosity and self-diffusivity develop different couplings to the degree of pairwise structural ordering of the liquid. We discuss how these couplings reflect dynamic heterogeneities. Finally, we note that the simulation data suggests how repulsive and attractive glasses may generally be characterized by two distinct levels of short-range structural order.

9 pages, 9 figures Submitted to The Journal of Chemical Physics

References in corpus (1)

• Excess entropy, Diffusivity and Structural Order in liquids with water-like anomalies

Cited by in corpus (8)

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• Viscoelasticity and Stokes-Einstein relation in repulsive and attractive colloidal glasses
• Cofinement, entropy, and single-particle dynamics of equilibrium hard-sphere mixtures
• Composition and concentration anomalies for structure and dynamics of Gaussian-core mixtures