Diffusion and the Mesoscopic Hydrodynamics of Supercooled Liquids

Abstract

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 macroscopic continuum hydrodynamics, is well satisfied for liquids under ordinary to high temperature conditions, even for solutes as small as the solvent. Diffusion in supercooled liquids near their glass transition temperature has been found to deviate by as much as 3 orders of magnitude from that predicted by the Stokes-Einstein Relation [1]. Based on the random first order transition theory [2-4], supercooled liquids possess a mosaic structure. The size- and temperature-dependence of the transport anomalies are quantitatively explained with an effective medium hydrodynamics model based on the microscopic theory of this mesoscale, mosaic structure.