Structural Crossover in Binary HardSphere Mixtures:Experiment and Theory
Abstract
In a onecomponent fluid the FisherWidom line distinguishes the region of the phase diagram where the total (pair) correlation function h(r) exhibits damped oscillatory decay at large separations r ,characteristic of dense... [ view full abstract ]
In a onecomponent fluid the FisherWidom line distinguishes the region of the phase diagram where the total (pair) correlation function h(r) exhibits damped oscillatory decay at large separations r ,characteristic of dense liquids, from that where the decay is monotonic, characteristic of gases and near critical fluids.
For binary fluid mixtures, in addition to a FisherWidom line, another crossover line is predicted when the two species are sufficiently different in size. The dominant wavelength of oscillations is the same for all three partial pair correlation functions h_{ij}(r) and is predicted to change from roughly the diameter of the large species to that of the small species along a sharp structural crossover line in the mixture phase diagram. From particleresolved experiments on binary hardsphere (HS) colloids, we demonstrate that crossover exists and that the location of the crossover line in the phase diagram is in quantitative agreement with the results of both theory and our MonteCarlo simulations. In contrast with earlier claims, we find that structural crossover is unrelated to percolation. We comment also on the behaviour of the true correlation length, extracted from the asymptotic large r decay of h(r), in onecomponent HS colloidal fluids at high volume fractions approaching the glass transition.
Authors

Robert Evans
(University of Bristol)
Topic Area
Challenges and advances in fluid phase equilibria
Session
Fluids  2 » Parallel Session  Advances in Fluid Phase Equilibria (16:40  Thursday, 7th September, Pentland Suite)
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