What causes the super-Arrhenius slowdown of supercooled liquids? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title · changed
Revision 1: What causes the super-Arrhenius slowdown of supercooled liquids
Revision 2: What causes the super-Arrhenius slowdown of supercooled liquids?
Plain
As a glass-forming liquid is cooled, the time its molecules take to rearrange grows by about 14 powers of ten over a narrow temperature range, much faster than the simple Arrhenius law (a fixed energy barrier) predicts. Which microscopic mechanism produces this growth is unknown.
Precise · changed · core
Revision 1: In molecular glass formers the structural relaxation time $\tau_\alpha(T)$ grows from about $1e-12\ \mathrm{s}$ in the high-temperature liquid to about $1e2\ \mathrm{s}$ at $T_g$, with an effective activation energy that increases on cooling; model liquids (Kob-Andersen Lennard-Jones mixture, polydisperse soft spheres) reproduce the onset of this growth. Competing explanations include random first-order transition theory (entropy-driven cooperative rearrangements), dynamic facilitation (kinetically constrained localized excitations) and elastic or frustration-based models. An answer is a theory that predicts $\tau_\alpha(T)$ and the associated growing length scales from the interaction potential and is singled out against the alternatives by equilibrium simulations near and below the experimental $T_g$. This is the root question of the topic; its working content is split into the sharper problems linked to it.
Revision 2: In molecular glass formers the structural relaxation time $\tau_\alpha(T)$ grows from about $10^{-12}\ \mathrm{s}$ in the high-temperature liquid to about $10^{2}\ \mathrm{s}$ at $T_g$, with an effective activation energy that increases on cooling; model liquids (Kob-Andersen Lennard-Jones mixture, polydisperse soft spheres) reproduce the onset of this growth. Competing explanations include random first-order transition theory (entropy-driven cooperative rearrangements), dynamic facilitation (kinetically constrained localized excitations) and elastic or frustration-based models. An answer is a theory that predicts $\tau_\alpha(T)$ and the associated growing length scales from the interaction potential and is singled out against the alternatives by equilibrium simulations near and below the experimental $T_g$. This is the root question of the topic; its working content is split into the sharper problems linked to it.
Settled by
A theory whose quantitative predictions for $\tau_{\alpha}(T)$, $\xi(T)$ and their relation are confirmed, and those of rival theories refuted, in swap-Monte-Carlo-equilibrated simulations below the experimental $T_{g}$.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
contested
Status note
Swap Monte Carlo has equilibrated model liquids below the experimental $T_{g}$ since about 2017, but as of 2026 no test has eliminated the main competing theories.
Posed since
(empty)

Decisions