Crossover to Potential Energy Landscape Dominated Dynamics in a Model Glass-forming Liquid

TL;DR

This study provides numerical evidence that below a certain temperature, the dynamics of a glass-forming liquid are dominated by the potential energy landscape, characterized by vibrational and transition behaviors between inherent structures.

Contribution

It demonstrates the crossover to landscape-dominated dynamics in a model glass-former and links the crossover temperature to the mode-coupling critical temperature.

Findings

Below $T_x$, dynamics are dominated by inherent structure transitions.

Transitions involve cooperative, string-like particle rearrangements.

$T_x$ is near the mode-coupling critical temperature $T_c$.

Abstract

An equilibrated model glass-forming liquid is studied by mapping successive configurations produced by molecular dynamics simulation onto a time series of inherent structures (local minima in the potential energy). Using this ``inherent dynamics'' approach we find direct numerical evidence for the long held view that below a crossover temperature, $T_x$, the liquid's dynamics can be separated into (i) vibrations around inherent structures and (ii) transitions between inherent structures (M. Goldstein, J. Chem. Phys. {\bf 51}, 3728 (1969)), i.e., the dynamics become ``dominated'' by the potential energy landscape. In agreement with previous proposals, we find that $T_x$ is within the vicinity of the mode-coupling critical temperature $T_c$. We further find that at the lowest temperature simulated (close to $T_x$), transitions between inherent structures involve cooperative, string like rearrangements of groups of particles moving distances substantially smaller than the average interparticle distance.