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Published Online June 30, 2005
Science DOI: 10.1126/science.1112399

Research Articles

Submitted on March 17, 2005
Accepted on May 24, 2005

Premelting at Defects Within Bulk Colloidal Crystals

Ahmed M. Alsayed 1, Mohammad F. Islam 1, Jian Zhang 1, Peter J. Collings 2, Arjun G. Yodh 1*

1 Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104-6396, USA.
2 Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104-6396, USA; Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081-1397, USA.

* To whom correspondence should be addressed.
Arjun G. Yodh , E-mail: yodh{at}physics.upenn.edu

Premelting is the localized loss of crystalline order at surfaces and defects for temperatures below the bulk melting transition. It can be thought of as the nucleation of the melting process. Premelting has been observed at the surfaces of crystals, but not within. We report observations of premelting at grain boundaries and dislocations within bulk colloidal crystals using real time video microscopy. The crystals are equilibrium close-packed three-dimensional colloidal structures made from thermally responsive microgel spheres. Particle tracking reveals increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. Our observations suggest interfacial free energy is the crucial parameter for premelting, in colloidal and atomic scale crystals.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Imaging the Sublimation Dynamics of Colloidal Crystallites.
J. R. Savage, D. W. Blair, A. J. Levine, R. A. Guyer, and A. D. Dinsmore (2006)
Science 314, 795-798
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Science. ISSN 0036-8075 (print), 1095-9203 (online)