Projects per year
Abstract
We report a detailed study, using stateoftheart simulation and theoretical methods, of the effective (depletion) potential between a pair of big hard spheres immersed in a reservoir of much smaller hard spheres, the size disparity being measured by the ratio of diameters q s/b. Small particles are treated grand canonically, their influence being parameterized in terms of their packing fraction in the reservoir nsr. Two Monte Carlo simulation schemesthe geometrical cluster algorithm, and staged particle insertionare deployed to obtain accurate depletion potentials for a number of combinations of q&le0.1 and nsr. After applying corrections for simulation finitesize effects, the depletion potentials are compared with the prediction of new density functional theory (DFT) calculations based on the insertion trick using the Rosenfeld functional and several subsequent modifications. While agreement between the DFT and simulation is generally good, significant discrepancies are evident at the largest reservoir packing fraction accessible to our simulation methods, namely, nsr=0.35. These discrepancies are, however, small compared to those between simulation and the much poorer predictions of the Derjaguin approximation at this nsr. The recently proposed morphometric approximation performs better than Derjaguin but is somewhat poorer than DFT for the size ratios and smallsphere packing fractions that we consider. The effective potentials from simulation, DFT, and the morphometric approximation were used to compute the second virial coefficient B2 as a function of nsr. Comparison of the results enables an assessment of the extent to which DFT can be expected to correctly predict the propensity toward fluidfluid phase separation in additive binary hardsphere mixtures with q&le0.1. In all, the new simulation results provide a fully quantitative benchmark for assessing the relative accuracy of theoretical approaches for calculating depletion potentials in highly sizeasymmetric mixtures.
Original language  English 

Article number  061136 
Number of pages  15 
Journal  Physical Review E 
Volume  84 
Issue number  6 
Early online date  20 Dec 2011 
DOIs  
Publication status  Published  Dec 2011 
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Projects
 1 Finished

Simulation Studies of Colloidal Phase Behaviour: Beyond Effective OneComponent Models
Wilding, N.
Engineering and Physical Sciences Research Council
4/08/08 → 3/08/11
Project: Research council
Equipment

High Performance Computing (HPC) Facility
Steven Chapman (Manager)
University of BathFacility/equipment: Facility