Abstract
Indications for a crossover between two distinct dynamical regimes at a temperature above the glass-transition temperature are presented for simple supercooled liquids. (i) Relating diffusion coefficient D and reorientational correlation times τ with viscosity η, a discontinuity for the temperature coefficient of τ/η or 1/Dη is observed, demonstrating the failure of the Stokes-Einstein relations for T<. (ii) Plotting NMR and dielectric correlation times on a reduced scale /T shows that a bifurcation of the two relevant processes in a supercooled liquid (α and β processes) appears for T<. is found at T/=1.18–1.28.
- Received 1 November 1989
DOI:https://doi.org/10.1103/PhysRevLett.65.1595
©1990 American Physical Society