Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface

TL;DR

This study explores how the energy landscape's stationary points relate to the fragility of supercooled Lennard-Jones mixtures, revealing that more fragile mixtures exhibit sharper increases in energy barriers and specific vibrational properties.

Contribution

It provides a detailed numerical analysis linking potential energy surface features to the fragility of supercooled liquids, highlighting new correlations with stationary point properties.

Findings

Fragility correlates with the sharpness of energy barrier increase.

Unstable mode properties vary with fragility.

Vibrational density of states relates to mixture fragility.

Abstract

We numerically investigated the connection between isobaric fragility and the properties of high-order stationary points of the potential energy surface in different supercooled Lennard-Jones mixtures. The increase of effective activation energies upon supercooling appears to be driven by the increase of average potential energy barriers measured by the energy dependence of the fraction of unstable modes. Such an increase is sharper, the more fragile is the mixture. Correlations between fragility and other properties of high-order stationary points, including the vibrational density of states and the localization features of unstable modes, are also discussed.