Structure and equation of state of interaction site models for disc-shaped lamellar colloids |
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Authors: | Dino Costa Jean-Pierre Hansen Ludger HarNau |
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Institution: | 1. Dipartimento di Fisica , Università di Messina , Contrada Papardo, C.P. 50, 98166 Messina, Italy;2. Department of Chemistry , University of Cambridge , Lensfield Road, Cambridge CB2 1EW, UK;3. Max-Planck-Institut für Metallforschung , Heisenbergstr. 3, D-70569 Stuttgart, Germany;4. Institut für Theoretische und Angewandte Physik , Universit?t Stuttgart , Pfaffenwaldring 57, D-70569 Stuttgart, Germany |
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Abstract: | We apply RISM (reference interaction site model) and PRISM (polymer-RISM) theories to calculate the site–site pair structure and the osmotic equation of state of suspensions of circular or hexagonal platelets (lamellar colloids) over a range of ratios of the particle diameter over thickness Dσ. Despite the neglect of edge effects, the simpler PRISM theory yields results in good agreement with the more elaborate RISM calculations, provided the correct form factor, characterizing the intramolecular structure of the platelets, is used. The RISM equation of state is sensitive to the number n of sites used to model the platelets, but saturates when the hard spheres, associated with the interaction sites, nearly touch; the limiting equation of state agrees reasonably well with available simulation data for all densities up to the isotropic–nematic transition. When properly scaled with the second virial coefficient, the equations of state of platelets with different aspect ratios Dσ nearly collapse on a single master curve. |
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