Qualitative change in structural dynamics of some glass-forming systems

Analysis of the temperature dependence of the structural relaxation time τα(T) in supercooled liquids revealed a qualitatively distinct feature - a sharp, cusplike maximum in the second derivative of logτα(T)at some Tmax. It suggests that the super-Arrhenius temperature dependence of τα(T) in glass-forming liquids eventually crosses over to an Arrhenius behavior at T<Tmax, and there is no divergence of τα(T) at nonzero T. Tmax can be above or below Tg, depending on the sensitivity of τ(T) to a change in the liquid's density quantified by the exponent γ in the scaling τα(T)∼exp(A/Tρ-γ). These results might turn the discussion of the glass transition in a different direction - toward the origin of the limiting activation energy for structural relaxation at low T.