8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.8Wed 711:10-14:00Calculation of hard sphere depletion potentialsDouglas Ashton, 1 Nigel Wilding, 2 Roland Roth, 3 and Robert Evans 41 Utrecht University, Debye Institute, PO Box 80000 3508 TA, Utrecht, Netherlands2 University of Bath, Bath, United Kingdom3 Universität Erlangen-Nürnberg, Erlangen, Germany4 University of Bristol, Bristol, United KingdomThe depletion potential describes the effective interaction, driven purely by entropy, betweentwo large colloidal particles immersed in a sea of small particles. Through the addition ofnon-adsorbing polymer, this interaction is used with great success to control the properties ofcolloidal dispersions. Therefore there is a strong incentive to obtain a clear theoretical picture ofthis force. While exact results exist for the case of ideal polymer (the Asakura-Oosawa potential)significant difficulties arise for both simulation and theory in the opposite limit of additive hardspheres. Through the application of specialised Monte Carlo algorithms, such as the geometriccluster algorithm [1] and staged insertion techniques [2], we have been able to accurately measurehard sphere depletion potentials for mixtures with large size ratios of 10:1 and above [3]. Fromthe consequent second virial coefficients these potentials also allow us to make predictions onthe likelihood of fluid-fluid demixing at various size ratios. While our results are generally ingood agreement with results from density functional theory we find a growing discrepancy at highsmall-particle volume fraction.[1] D. J. Ashton, J. Liu, E. Luijten, N. B. Wilding, J. Chem. Phys. 133, 194102 (2010).[2] D. J. Ashton and N. B. Wilding, Mol. Phys. online, iFirst (2010).[3] D. J. Ashton, N. B. Wilding, R. Evans, R. Roth, In preparation.8