Berlin 2008 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 10: Glasses III (joint session DF/DY)
DF 10.7: Vortrag
Mittwoch, 27. Februar 2008, 16:00–16:15, EB 407
Crystal precursor nucleation: A connection between crystallization and vitrification. — •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 (crystallization, 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. We investigated the solidification scenario in suspensions of colloidal hard spheres for three polydispersities between 4.8% and 5.8%, from near freezing to near the glass transition. We identify four stages in the crystallization process: (i) an induction stage where large numbers of precursor structures are observed; (ii) a conversion stage as precursors are converted to close packed structures; (iii) a second nucleation stage; and (iv) a ripening stage. Near the glass transition the crystallization process is entirely frustrated, and the sample is locked into a compressed crystal precursor structure. Interestingly neither polydispersity nor volume fraction significantly influence the precursor stage, suggesting that the crystal precursors are present in all solidifying samples. We speculate that these precursors are related to the dynamical heterogeneities observed in a number of dynamical studies linking the two processes of crystallization and vitrification. JCP 127, 084505 (2007)