The recently discovered scaling law for the relaxation times,tau(T,V) = ZETA{Tv~(gamma)),where T is temperature and v the specific volume,is derived by a revision of the entropy model of the glass transition dynamics originally proposed by Avramov [J.Non-Cryst.Solids 262,258 (2000)].In this modification the entropy is calculated by an alternative route.The resulting expression for the variation of the relaxation time with T and v is shown to accurately fit experimental data for several glass-forming liquids and polymers over an extended range encompassing the dynamic crossover.From this analysis,which is valid for any model in which the relaxation time is a function of the entropy,we find that the scaling exponent gamma can be identified with the Gruneisen constant.
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