Qualitative change in structural dynamics of some glass-forming systems

Analysis of temperature dependence of structural relaxation time $\tau (T)$ in supercooled liquids revealed a qualitatively distinct feature - a sharp, cusp-like maximum in the second derivative of log $\tau _{\mathrm{\alpha }}(T)$ at some $T_{max}$. It suggests that the super-Arrhenius temperature dependence of $\tau_{\mathrm{\alpha }}(T)$ in glass-forming liquids eventually crosses over to an Arrhenius behavior at \textit{T\textless T}$_{max}$, and there is no divergence of $\tau_{\mathrm{\alpha }}(T)$ at non-zero $T$. $T_{max}$ can be above or below $T_{g}$, depending on sensitivity of $\tau (T)$ to change in liquid's density quantified by the exponent $\gamma $ in the scaling $\tau_{\mathrm{\alpha }}(T)$ \textasciitilde exp($A/T\rho^{\mathrm{-\gamma }})$. These results might turn the discussion of the glass transition to the new avenue -- the origin of the limiting activation energy for structural relaxation at low $T$.