Dynamics of glass-forming liquids. V. On the link between molecular dynamics and configurational entropy

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We compare dielectric relaxation τ(T) data of several low molecular weight glass-forming liquids with the predictions of the Adam-Gibbs theory using experimental data for the configurational entropy Sc(T). Combination of Adam-Gibbs and Vogel-Fulcher equations yields an expression for Sc(T) which can be compared with experimental data. Good agreement is found for a range of temperatures near Tg<T<TB which depends on the fragility of the liquid and on the presence of a β relaxation. For fragile liquids, TB coincides with a qualitative change in the temperature dependence of the relaxation time scale or viscosity, with the temperature Tβ, where Johari-Goldstein-type β processes tend to merge into the α process, and with other crossover temperatures. For nonfragile liquids, TB/Tg increases, and the deviations from the Adam-Gibbs equation weaken or disappear altogether. The significance of TB, and of the Sc(T) temperature dependence implied by the Vogel-Fulcher theory fitting, are discussed in terms of the landscape paradigm.

Original languageEnglish (US)
Pages (from-to)9016-9026
Number of pages11
JournalJournal of Chemical Physics
Issue number21
StatePublished - Jun 1 1998


ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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