Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 10: SYM Phase Transformations in Metallic Melts IV
MM 10.4: Vortrag
Montag, 25. Februar 2008, 17:15–17:30, H 1058
Crystal nucleation in colloidal model systems - Is Classical Nucleation Theory still state of the art? — •Hans Joachim Schöpe1, Gary Bryant2, and William van Megen2 — 1Johannes Gutenberg-Universität Mainz, Institut für Physik, Staudinger Weg 7, 55099 Mainz, Deutschland — 2Department of Applied Physics, Royal Melbourne Institute of Technology, GPO Box 2476V, Melbourne 3001, Australia
A complete understanding of the solidification process (nucleation, crystal growth, ripening, vitrification) is one of the long-standing problems in condensed matter physics. The use of colloidal model systems provides an ideal controlled experimental system to reduce this lack of knowledge because the particle movement is much slower than in atomic systems and the crystallisation process can be monitored using optical investigations. Here we present systematic measurements of the solidification kinetics and of the phase behaviour as a function of the particle concentration in nominally one component colloidal model systems of spherical particles. Interestingly we observe a two step behaviour in the nucleation kinetics which was also recently observed in crystallization of proteins and simple atomic liquids.: (i) an induction stage where large numbers of precursor structures are observed; (ii) a conversion stage as precursors are converted to close packed structures. This behaviour is in contrast to the alternative of ordering and densifying at once as assumed in the classical picture of crystallization.
PRL 96, 175701 (2006)