Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: POSTERS Driven Soft Matter

CPP 20.26: Poster

Wednesday, February 27, 2008, 16:00–18:30, Poster A

Confined colloidal crystals. — Ana Barreira Fontecha, •Hans Joachim Schöpe, and Thomas Palberg — Johannes Gutenberg-Universität Mainz, Institut für Physik, Staudinger Weg 7, 55099 Mainz, Deutschland

The packing of spheres in confined geometry is of fundamental and practical interest for logistics, mathematics, condensed matter physics. For colloids in the bulk bcc packing is observed at long ranged repulsions, while fcc and hcp for short ranged interactions. Restricting the available space leads to adaptations of these structures to the symmetry of the confinement and a rich variety is found as a function of colloid packing fraction and confinement dimension. Their practical importance lies within their use as photonic and phononic materials, while at the same time there is a fundamental interest to understand this diversity in terms of thermodynamics, kinetics and the influence of external forces. We study the confinement of colloidal latex spheres subjected to lateral compression in a thin wedge, which allows us to investigate the structural changes taking place in the transition from 2 to 3 dimensions. In this presentation we extend former experimental work presenting new crystalline structures. In particular, we report on a vertically oriented hexagonally close packed (hcp) structure, a prism structure with triangular basis, a prism structure with square basis and a structure alternating between triangular and square symmetry. Following the maximum packing criterion we show that all these structures have their own range of maximum stability as function of the plate distance. PRE 76, 050402R (2007)