Efficient measurement of linear susceptibilities in molecular simulations: Application to aging supercooled liquids

TL;DR

This paper introduces a novel method for measuring time-dependent linear susceptibilities in molecular simulations that avoids traditional nonequilibrium techniques, providing more accurate insights into aging supercooled liquids.

Contribution

The authors present an exact reformulation that allows susceptibility measurements from unperturbed trajectories, improving accuracy over previous methods.

Findings

Revealed larger deviations from fluctuation-dissipation relations in Lennard-Jones liquids.

Found qualitative disagreements with earlier results for silica.

Demonstrated the method's effectiveness in aging supercooled liquids.

Abstract

We propose a new method to measure time-dependent linear susceptibilities in molecular simulations, which does not require the use of nonequilibrium simulations, subtraction techniques, or fluctuation-dissipation theorems. The main idea is an exact reformulation of linearly perturbed quantities in terms of observables accessible in unperturbed trajectories. We have applied these ideas to two supercooled liquids in their nonequilibrium aging regime. We show that previous work had underestimated deviations from fluctuation-dissipation relations in the case of a Lennard-Jones system, while our results for silica are in qualitative disagreement with earlier results.