Towards a Unification of Theories of the Glass Transition?*

Our understanding of the glass transition is hampered by the astronomical timescales required to discriminate competing theoretical approaches. Recently, considerable progress has been made in obtaining data at unprecedented degrees of supercooling [1], yet theoretical approaches based on dynamical or thermodynamical standpoints still describe the available data.

Here we make the case that the dynamical phase transition of dynamic facilitation theory, is in fact compatible with thermodynamic interpretations such as random first order transition theory. We use trajectory sampling in experiments and simulations to show that the dynamical transition has a structural character [2,3] and reweight these data to extend the dynamical phase transition to deeper supercooling than previously accessed [4]. The inactive phase exhibits a lower entropy than the active phase (normal supercooled liquid) which falls only slowly as a function of temperature, as noted by Kauzmann in the context of supercooled liquids and their crystal. We find evidence that the dynamical phase transition has a lower critical point close to the Kauzmann temperature where the configurational entropy is predicted to become small in thermodynamic theories. In this picture, the dynamical phase transition of facilitation is thus incorporated into a thermodynamic picture of sub-extensive entropy at low temperature [5].

[1] Royall CP, Turci F, Russo J, Tatsumi S and Robinson JFE, J. Phys.: Condens. Matter 30 363001 (2018).

[2] Speck T, Malins A and Royall CP, Phys. Rev. Lett. 109 195703 (2012).

[3] Pinchaipat R, Campo M, Turci F, Hallet JE, Speck T, and Royall CP, Phys. Rev. Lett. 119 028004 (2017).

[4] Turci F and Royall CP and Speck T, Phys. Rev. X 7 031028 (2017).

[5] Royall CP, Turci F and Speck T, J. Chem. Phys. 153 090901 (2020).