When glasses formed by cooling at different rates are heated at the same rate, they show different shapes of the glass to liquid transition endotherm in their Cp-T plot and different onset temperatures of the Cp-endotherm. (This temperature is taken as the glass to liquid transition temperature. To prevent confusion we denote it as Tg l.) According to the phenomenology of glass to liquid transition, (i) a glass formed by slower cooling shows on heating a higher Tg lthan a glass formed by rapid cooling and (ii) the Cp-endotherm fs shape changes and its enthalpy recovery overshoot becomes higher. But a recent study arbitrarily asserted the opposite, namely, that a glass formed by slower cooling of a liquid has a lower Tg l, and this feature is "a typical signature of a glass transition". By using that gsignature h the study concluded that an ill-defined state of solid water has a gsecond Tg h (Tg lin the terminology here) at 116 K. The assertion caused us to perform a calorimetric study of the glass to liquid transition phenomenon in eight materials by using the same cooling/heating protocols that had led to the assertion of the signature. Our study confirms the already known glass phenomenology. Therefore, ga typical signature for aglass transition h is false, and the second Tg(or Tg l) at 116 K based on the study of an ill-defined solidwater (formed by annealing the pressure-collapsed state of ice) was phenomenologically-mistaken. Ina different context, we quantify the dependence of Tg lon the cooling rate and compare the effect of slow cooling against the effects of annealing (ageing) on the properties of the glassy state. The study hasadverse consequences for some models of the structure of water.
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.