Colloquium 6/6/2011

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Hans Joachim Schöpe

Johannes Gutenberg-Universität Mainz,
Institut für Physik,
Staudinger Weg 7, 55099 Mainz, Deutschland

Crystallization of colloidal spheres

Understanding the crystallization process of a metastable melt is a long standing fundamental problem of condensed matter physics. Furthermore it is quite important for designing crystalline materials in metallurgy, photonics or biotechnology, because a detailed knowledge and control of the crystallization process is mandatory to develop novel crystalline materials. The crystallization process is given by a complex interplay of crystal nucleation, growth and ripening. Further more crystal nucleation is dominated by heterogeneous nucleation in most cases, especially at low metastabilities. A great deal of progress understanding the process that drives a metastable melt into solid state has been made in recent years using colloidal suspensions as model systems studying crystallization and vitrification. Because of their large size, both the dynamics and kinetics of these systems are experimentally much more accessible than it is the case for atomic and molecular systems. Still, close analogies to atomic systems are observed which can be exploited to address questions not accessible in atomic solidification. While some observation can be describes and analyzed within the classical picture of crystallization some others show clear deviations. I will show an overview of our experiments investigating the crystallization scenario in colloidal hard and charged spheres under various conditions using light scattering and microscopy techniques, determining among others induction times, nucleation rate densities and crystal growth velocities for both homogeneous and heterogeneous nucleation as function of metastability.