# Solid-like mean-square displacement in glass-forming liquids

## TL;DR

This paper demonstrates that the mean-square displacement in a modified Lennard-Jones glass-forming liquid aligns with the random barrier model, revealing simple underlying dynamics in complex glassy systems.

## Contribution

Introduces a crystallization-resistant Lennard-Jones mixture and shows its low-temperature dynamics fit the RBM without shape parameters.

## Key findings

- Mean-square displacement matches RBM predictions
- Simple hopping model explains complex glass dynamics
- GPU simulations validate the model's applicability

## Abstract

It was recently shown that the real part of the frequency-dependent fluidity for several glass-forming liquids of different chemistry conforms to the prediction of the random barrier model (RBM) devised for ac electrical conduction in disordered solids [S. P. Bierwirth \textit{et al.}, Phys. Rev. Lett. {\bf 119}, 248001 (2017)]. Inspired by these results we introduce a crystallization-resistant modification of the Kob-Andersen binary Lennard-Jones mixture for which the results of extensive graphics-processing unit (GPU)-based molecular-dynamics simulations are presented. We find that the low-temperature mean-square displacement is fitted well by the RBM prediction, which involves no shape parameters. This finding highlights the challenge of explaining why a simple model based on hopping of non-interacting particles in a fixed random energy landscape can reproduce the complex and highly cooperative dynamics of glass-forming liquids.