Deep glassy state dynamic data challenge glass models: Elastic models

Abstract

There is increasing experimental evidence that suggests that the dynamics of glass forming liquids do not diverge at finite temperature above zero Kelvin, at the same time there has been recent progress in the development of non-diverging glass transition models. In this work we examine two non-diverging models: the elastically collective nonlinear Langevin equation theory (ECNLE) and the shoving model, both of which relate an energy barrier in the glass formation process with elastic motion at small scales. The models are evaluated in comparison with the non-diverging dynamic data obtained in the deep glassy state (very stable) for a 20-million-year-old (20 Ma) ancient amber and for a vapor deposited amorphous Teflon obtained previously. We find that although both models are in qualitative agreement with the dynamic data for the two stable glasses, they still overestimate the actual relaxation times for the deep glassy state below the nominal glass transition temperature and for conditions corresponding to the equilibrium state or in a state in which the glass relaxation times are upper bounds to the equilibrium values.

Keywords

• Glass transition
• Diverging time-scales
• Non-diverging time-scales
• ECNLE model
• Shoving model
• Glass dynamics