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Issue 15, 2012
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Enhancing tracer diffusivity by tuning interparticle interactions and coordination shell structure

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Abstract

This study uses a combination of stochastic optimization, statistical mechanical theory, and molecular simulation to test the extent to which the long-time dynamics of a single tracer particle can be enhanced by rationally modifying its interactions—and hence static correlations—with the other particles of a dense fluid. Specifically, a simulated annealing strategy is introduced that, when coupled with test-particle calculations from an accurate density functional theory, finds interactions that maximize either the tracer's partial molar excess entropy or a related pair-correlation measure (i.e., two quantities known to correlate with tracer diffusivity in other contexts). The optimized interactions have soft, Yukawa-like repulsions, which extend beyond the hard-sphere interaction and disrupt the coordination-shell cage structure surrounding the tracer. Molecular and Brownian dynamics simulations find that tracers with these additional soft repulsions can diffuse more than three times faster than bare hard spheres in a moderately supercooled fluid, despite the fact that the former appear considerably larger than the latter by conventional definitions of particle size.

Graphical abstract: Enhancing tracer diffusivity by tuning interparticle interactions and coordination shell structure

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Article information


Submitted
11 Oct 2011
Accepted
08 Nov 2011
First published
23 Nov 2011

Soft Matter, 2012,8, 4083-4089
Article type
Paper

Enhancing tracer diffusivity by tuning interparticle interactions and coordination shell structure

J. Carmer, G. Goel, M. J. Pond, J. R. Errington and T. M. Truskett, Soft Matter, 2012, 8, 4083
DOI: 10.1039/C1SM06932B

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