ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Coupling model analyses of short-time relaxation data of glycerol from quasielastic neutron scattering and ortho-terphenyl (OTP) by molecular dynamic simulation are shown to account for both the time dependence of the correlation function and its temperature dependence. The latter is expressible over a limited temperature range as an Arrhenius relation with an apparent activation energy for the fast α-relaxation process, with EA=6.2 and 3.9 kcal/mol for glycerol and OTP, respectively. The viscosities of these glass formers have also been measured up to temperatures sufficiently high that the mean viscosity relaxation time, 〈τη(T)〉, becomes short, approaching the crossover time, tc(approximate)2 ps, of the coupling model. When this condition is realized, 〈τη(T)〉 becomes comparable to τD(T) in both magnitude and temperature dependence. Hence, the asymptotic high temperature activation energy of 〈τη(T)〉 approximately equals the apparent activation energy of τD. The experimental data, supporting this connection between macroscopic variables such as viscosity and microscopic dynamics from neutron scattering and molecular dynamics simulation, indicate the significance of the fast α-relaxation process in both fragile and strong liquids.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.473215
