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    COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
                              CSI 898-Sec 001  
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          Spatially Correlated Dynamics in Glass-forming Liquids:  
                     New Results from Computer Simulation

                              Sharon C. Glotzer
            Polymers Division and Center for Theoretical and 
         Computational Materials Science, NIST, Gaithersburg, MD

Molecular dynamics (MD) simulations allow us to study detailed molecular
motions of liquids approaching their glass transition. Using MD, we are
investigating these motions to determine the nature of the dramatic slowing
down observed in "glassy" liquids. To this end, we define a  correlation
function that quantifies the spatial correlations of local equilibrium
fluctuations of single-particle displacements in liquids and amorphous
materials. Using this function, we show with extensive molecular dynamics
simulations of several supercooled, glassforming liquids that the particle
displacements are spatially correlated over a range and time scale that both
grow with decreasing temperature as the liquid is cooled. We find that
particles tend to move cooperatively in glassy liquids, forming large,
"string-like" clusters  in both the Lennard-Jones mixture and polymer melts
under study.

                       Monday , September 14 1998
                                 4:30 pm
                        Room 206, Science & Tech. I

Refreshments will be served.
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