The aim of this project was to study aging in glasses by following the evolution of packing and geometry in a colloidal glass. Our group has already found that the dynamics of aging are heterogeneous in both time and space. Here we focus our confocal microscopes and our attention on some static properties of glasses. What follows is some background to help explain the motivation behind our approach. You can also get the papers for more detailed information. Colloidal suspensions are good model systems for atomic and molecular materials. For example we can easily obtain a colloidal crystal by simply increasing the packing fraction above Φ So it would seem that in hard sphere systems packing optimization is the prime directive, one that is always followed... To explore packing in three dimensions one must consider at least four colloids (with three colloids you always only define a plane, with two a line and with one... a point!). When trying to pack these colloids as efficiently as possible one ends up with a tetrahedron such as the one shown at the top of the page. By doing so one can obtain a (local) packing fraction of Φ It turns out that tetrahedra do not tile space in 3D (on the right) just like pentagons do not tile a 2D surface (on the left). The competition between the drive to optimize packing and the necessity to tile space can be thought of as a sort of With this project we studied the evolution of tetrahedral packing in an aging colloidal glass hoping to explain the latter in terms of the former. Our results can be summarized as follows: - Aging slows down the dynamics of the system: particles slow down with time.
- Tetrahedral structure is somewhat related to dynamcis: in general, the looser and the more irregular a tetrahedron, the more mobile are the colloids that form it.
- Yet
*surprisingly*, the distribution of tetrahdedral structural characteristics does not age with time!
## Some papers on this subjectYou may be interested in reading our papers for a fuller discussion. **"Correlations of structure and dynamics in an aging colloidal glass"** GC Cianci, RE Courtland, and ER Weeks, Solid State Comm.**139**, 599-604 (2006)**"Invariance of structure in an aging colloidal glass"** GC Cianci, RE Courtland, and ER Weeks, AIP Conf. Proc. 832:*Flow Dynamics: The Second International Conference on Flow Dynamics*, eds. M Tokuyama & S Maruyama, pp. 21-25 (2006).
This work has been primarily funded by NASA (NAG3-2728). For more information, please contact Eric Weeks: <weeks(at)physics.emory.edu> |