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 l iquids. Although the magnitude of these fluctuations changes little wi th temperature, the sensitivity of molecular motion to changes in dens ity 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 proc esses and the enhancement of translational diffusion in deeply superco oled liquids. In particular, the entropy model correctly predicts that probe translation near T-g in o-terphenyl and polystyrene is more enh anced than in polyisobutylene. (C) 1998 Elsevier Science B.V. All righ ts reserved.