Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Poster: Colloids and Complex Liquids

CPP 38.20: Poster

Mittwoch, 16. März 2011, 17:00–19:00, P2

Crystallization of charged colloids in extreme confinement — •Tetyana Kromer-Vovk, Nadezhda Gribova, and Axel Arnold — ICP, Universität Stuttgart, Germany

Freezing effects in spatially confined fluids and colloidal dispersions receive strong scientific interest over the last decades. Confining surfaces can be found in many contexts like the inner walls of porous materials or in a blood cell. In 3D freezing is a first-order phase transition between liquid and solid phase, while the phase behavior in 2D systems is more complicated since no real long-range translational order exists. The theory predicts a hexatic phase with short-range translational and quasi-long orientational order between liquid and solid. Although several works reported the existence of a hexatic phase in such systems, there still remains debate on the exact nature of the transition.

In our work we present MD simulations of a system of charged colloids in confinement using the ESPResSo software package. We investigated the phase behavior of a two layers system confined between parallel neutral walls. We studied various parameters to check for the presence of a hexatic phase. We find practically no energy barrier to nucleation, clearly showing that the freezing behavior differs from the bulk nucleation scenario. However, instead of an intermediate hexatic phase we find only a region of pronounced crystal-liquid coexistence. We also investigate the influence of various fixed crystal seeds as templates for the crystal phase. The seed enhances the phase separation and through this gives the impression of nucleation around the seed.