Thermodynamics of Coarse Grained Models of Super-Cooled Liquids

TL;DR

This paper defends the use of kinetically constrained coarse grained models to understand the thermodynamics of super-cooled liquids, particularly addressing criticisms about heat capacity predictions and emphasizing the importance of model parameters.

Contribution

It clarifies how coarse grained models can accurately describe heat capacity discontinuities when parameters are properly considered, countering previous objections.

Findings

Coarse grained models can explain heat capacity differences between fragile and strong glasses.

Parameters associated with coarse graining are crucial for accurate thermodynamic predictions.

The approach aligns with experimental observations when these parameters are included.

Abstract

In recent papers, we have argued that kinetically constrained coarse grained models can be applied to understand dynamic properties of glass forming materials, and we have used this approach in various applications that appear to validate this view. In one such paper [J.P. Garrahan and D. Chandler, Proc. Nat. Acad. Sci. USA 100, 9710 (2003)], among other things we argued that this approach also explains why the heat capacity discontinuity at the glass transition is generally larger for fragile materials than for strong materials. In the preceding article, Biroli, Bouchaud and Tarjus (BB&T) [cond-mat/0412024] have objected to our explanation on this point, arguing that the class of models we apply is inconsistent with both the absolute size and temperature dependence of the experimental specific heat. Their argument, however, neglects parameters associated with the coarse graining. Accounting for these parameters, we show here that our treatment of dynamics is not inconsistent with heat capacity discontinuities.