Diffusion and the mesoscopic hydrodynamics of supercooled liquids

The description of molecular motion by macroscopic hydrodynamics has a long and continuing history. The Stokes-Einstein relation between the diffusion coefficient of a solute and the solvent viscosity predicted using macrosco pic continuum hydrodynamics is well satisfied for liquids under ordinary to high-temperature conditions. even for solutes as small as the solvent. Dif fusion in supercooled liquids near their glass transition temperature has b een found to deviate by as much as 3 orders of magnitude from that predicte d by the Stokes-Einstein Relation [J. Chem. Phys. 1996, 104, 7210].(1) On t he basis of the random first-order transition theory [Phys. Rev. A 1987, 35 , 3072, Phys. Rev. A 1989, 40, 1045, and Proc. Natl. Acad. Sci. U.S.A. 2000 , 97, 2990],(2-4) supercooled liquids possess a mosaic structure. The size- and temperature-dependence of the transport anomalies are quantitatively e xplained with an effective medium hydrodynamics model based on the microsco pic theory of this mesoscale, mosaic structure.