Can density or entropy fluctuations explain enhanced translational diffusion in glass-forming liquids?

Density and entropy fluctuations which are present in all equilibrium liquids may explain several experimental observations in supercooled liquids. Although the magnitude of these fluctuations changes little with temperature, the sensitivity of molecular motion to changes in density and entropy increases strongly as the glass transition temperature (T-g) is approached from above. It is shown that density and entropy fluctuations can plausibly account for non-exponential relaxation processes and the enhancement of translational diffusion in deeply supercooled liquids. In particular, the entropy model correctly predicts that probe translation near T-g in o-terphenyl and polystyrene is more enhanced than in polyisobutylene. (C) 1998 Elsevier Science B.V. All rights reserved.