Relaxation dynamics in fluids of platelike colloidal particles - Condensed Matter > Soft Condensed MatterReportar como inadecuado

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Abstract: The relaxation dynamics of a model fluid of platelike colloidal particles isinvestigated by means of a phenomenological dynamic density functional theory.The model fluid approximates the particles within the Zwanzig model ofrestricted orientations. The driving force for time-dependence is expressedcompletely by gradients of the local chemical potential which in turn isderived from a density functional - hydrodynamic interactions are not takeninto account. These approximations are expected to lead to qualitativelyreliable results for low densities as those within the isotropic-nematictwo-phase region. The formalism is applied to model an initially spatiallyhomogeneous stable or metastable isotropic fluid which is perturbed byswitching a two-dimensional array of Gaussian laser beams. Switching on thelaser beams leads to an accumulation of colloidal particles in the beamcenters. If the initial chemical potential and the laser power are large enougha preferred orientation of particles occurs breaking the symmetry of the laserpotential. After switching off the laser beams again the system can followdifferent relaxation paths: It either relaxes back to the homogeneous isotropicstate or it forms an approximately elliptical high-density core which iselongated perpendicular to the dominating orientation in order to minimize thesurface free energy. For large supersaturations of the initial isotropic fluidthe high-density cores of neighboring laser beams of the two-dimensional arraymerge into complex superstructures.

Autor: Markus Bier, Rene van Roij


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