Publica
Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Statics and dynamics of colloidpolymer mixtures near their critical point of phase separation: A computer simulation study of a continuous AsakuraOosawa model
 The Journal of chemical physics 130 (2009), No.6, Art. 064906, 14 pp. ISSN: 00219606 

 English 
 Journal Article 
 Fraunhofer ITWM () 
Abstract
We propose a new coarsegrained model for the description of liquidvapor phase separation of colloidpolymer mixtures. The hardsphere repulsion between colloids, and between colloids and polymers, which is used in the wellknown Asakura–Oosawa (AO) model, is replaced with Weeks–Chandler–Andersen potentials. Similarly, a soft potential of height comparable to thermal energy is used for the polymerpolymer interaction, rather than treating polymers as ideal gas particles. It is shown by grandcanonical Monte Carlo simulations that this model leads to a coexistence curve that almost coincides with that of the AO model and that the Ising critical behavior of static quantities is reproduced. Then the main advantage of the model is exploited—its suitability for Molecular Dynamics simulations—to study the dynamics of mean square displacements of the particles, transport coefficients such as the selfdiffusion and interdiffusion coefficients, and dynamic structure factors. While the selfdiffusion of polymers increases slightly when the critical point is approached, the selfdiffusion of colloids decreases and at criticality the colloid selfdiffusion coefficient is about a factor of 10 smaller than that of the polymers. Critical slowing down of interdiffusion is observed, which is qualitatively similar to symmetric binary LennardJones mixtures, for which no dynamic asymmetry of selfdiffusion coefficients occurs.