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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. A combined molecular dynamics and Monte Carlo study of the approach towards phase separation in colloidpolymer mixtures
 Journal of Physics. Condensed Matter 22 (2010), Nr.10, Art. 104120 ISSN: 09538984 

 Englisch 
 Zeitschriftenaufsatz 
 Fraunhofer ITWM () 
Abstract
A coarsegrained model for colloidpolymer mixtures is investigated where both colloids and polymer coils are represented as pointlike particles interacting with spherically symmetric effective potentials. Colloidcolloid and colloidpolymer interactions are described by WeeksChandlerAndersen potentials, while the polymerpolymer interaction is very soft, of strength k(B)T/2 for maximum polymerpolymer overlap. This model can be efficiently simulated both by Monte Carlo and molecular dynamics methods, and its phase diagram closely resembles that of the wellknown AsakuraOosawa model. The static and dynamic properties of the model are presented for systems at critical colloid density, varying the polymer density in the onephase region. Applying LeesEdwards boundary conditions, colloidpolymer mixtures exposed to shear deformation are considered, and the resulting anisotropy of correlations is studied. Whereas for the considered shear rate, (gamma) over dot = 0.1, radial distribution functions and static structure factors indicate only small structural changes under shear, an appropriate projection of these correlation functions onto spherical harmonics is presented that allows us to directly quantify the structural anisotropies. However, the considered shear rate is probably not high enough to see anisotropies in static structure factors at small wavenumbers that have been predicted by Onuki and Kawasaki (1979 Ann. Phys. 121 456) for the critical behavior of systems under shear. The anomalous dependence of the polymer's selfdiffusion constant on polymer density is referred to the clustering of the colloid particles when approaching the critical point.