A single relaxation time description for glasses and their liquid state

We use relaxation data taken out of equilibrium on glasses of different stability and equilibrium relaxation times from the supercooled liquid to propose a common description for both liquid and glass states. Using ultrafast scanning calorimetry, the accessible timescales of the glass are expanded to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. Surprisingly, both the liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws derived for the liquid. This work provides a strong connection between the glass and liquid states.