SCIENCE AT THE EDGE SEMINAR
             http://www.pa.msu.edu/seminars/edge/

            11:30 A.M., Friday, September 20, 2002
                Room 208 BIOCHEMISTRY Building
    Refreshments served at 11:15 in Room 208 Biochemistry Building

        Supercooled Liquids as Nanostructured Complex Fluids

            Sharon C. Glotzer, University of Michigan

Abstract:
There has been a great deal of renewed interest in recent years in the
behavior of liquids near their glass transition.  A remarkable and seemingly
ubiquitous feature of such liquids, which is not yet understood, is the
spatially heterogeneous nature of their dynamics.  Computer simulations and
experiments have shown that, on cooling, liquids become spatially
dynamically heterogeneous, with dynamically correlated regions that extend
over distances of several nanometers or more near the glass transition
temperature.  In colloidal suspensions, recent experiments have demonstrated
that dynamically correlated regions can extend over hundreds of microns.
In this talk, we describe our molecular dynamics simulation studies that
delve into the nature of spatially heterogeneous dynamics in supercooled
liquids, and provide insight into the details of molecular motion.  We show
how individual cooperatively rearranging groups of molecules combine to form
larger, more complex dynamical structures.  Using several new computational
diagnostics, we demonstrate how dynamically correlated regions emerge and
grow on cooling.   We discuss the nature of this correlated motion and how
it may relate to local short-range and intermediate range structure, and
present a new  statistical mechanical framework suitable for describing
spatially heterogeneous dynamics in liquids.