Grzegorz Szamel of Colorado State University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to investigate the dynamics of molecules in quiescent and driven glassy fluids. Earlier studies showed that, upon approaching the glass transition, the dynamics become not only slower but also increasingly heterogeneous. Recent experiments suggested that the dynamic heterogeneity depends on the character of intermolecular interactions. The current work employs both computational and theoretical methods to analyze the dynamic heterogeneity in fluids with repulsive and attractive interactions. In addition, Szamel and his coworkers work to elucidate the connection between dynamic heterogeneity and slow dynamics. In the area of driven glassy fluids, the initial goal is to investigate long range correlations induced by the flow. The long term goal is to develop a theory for the dynamics in driven colloidal glassy fluids applicable to both thermal and athermal systems.
Upon sufficiently fast supercooling or densification, a great variety of fluids undergo a transformation to an amorphous solid state. This transformation is commonly referred to as the glass transition. Materials obtained in this process, especially polymeric and metallic glasses, have many practical applications. However, the very nature of the glass transition is still hotly debated. It is known that upon approaching the glass transition, the dynamics of the fluid slows down in a surprisingly non-uniform way. The role of this so-called dynamic heterogeneity, however, is not understood. Professor Szamel and his group characterize the non-uniform dynamics of glassy fluids and investigate its relation to the glass transition. Complex materials are often probed or ordered by imposing non-uniform flow. In particular, shear flow is known to melt glasses made of colloidal particles. Professor Szamel's research will characterize this process and relate the behavior of quiescent and flowing glassy colloidal suspensions.
