Characterization of the Dynamics of Glass-forming Liquids from the Properties of the Potential Energy Landscape

TL;DR

This paper presents a framework using a master equation approach to understand the dynamics of glass-forming liquids by analyzing the properties of their potential energy landscapes, linking landscape features to strong or fragile behavior.

Contribution

It introduces a novel master equation-based method to connect potential energy landscape properties with glassy liquid dynamics, validated through atomic cluster simulations.

Findings

Dynamics dominated by low-lying minima lead to strong glass behavior.

Limited exploration of the landscape results in fragile behavior.

The approach captures key features of glassy dynamics.

Abstract

We develop a framework for understanding the difference between strong and fragile behavior in the dynamics of glass-forming liquids from the properties of the potential energy landscape. Our approach is based on a master equation description of the activated jump dynamics among the local minima of the potential energy (the so-called inherent structures) that characterize the potential energy landscape of the system. We study the dynamics of a small atomic cluster using this description as well as molecular dynamics simulations and demonstrate the usefulness of our approach for this system. Many of the remarkable features of the complex dynamics of glassy systems emerge from the activated dynamics in the potential energy landscape of the atomic cluster. The dynamics of the system exhibits typical characteristics of a strong supercooled liquid when the system is allowed to explore the full configuration space. This behavior arises because the dynamics is dominated by a few lowest-lying minima of the potential energy and the potential energy barriers between these minima. When the system is constrained to explore only a limited region of the potential energy landscape that excludes the basins of attraction of a few lowest-lying minima, the dynamics is found to exhibit the characteristics of a fragile liquid.