Mechanical Properties of Glass Forming Systems

TL;DR

This paper investigates the mechanical properties of glass forming systems in an intermediate temperature range, using Monte Carlo and Molecular Dynamics methods to analyze their elastic moduli and behavior.

Contribution

It introduces an efficient Monte Carlo approach and an alternative Molecular Dynamics method to compute shear moduli, revealing the complex viscoelastic nature of glass formers.

Findings

Elastic moduli are finite at short times and vanish at long times.

Glass forming systems are not typical viscous fluids but exhibit mixed solid-like and liquid-like properties.

Comparison of Monte Carlo and Molecular Dynamics results enhances understanding of their mechanical behavior.

Abstract

We address the interesting temperature range of a glass forming system where the mechanical properties are intermediate between those of a liquid and a solid. We employ an efficient Monte-Carlo method to calculate the elastic moduli, and show that in this range of temperatures the moduli are finite for short times and vanish for long times, where `short' and `long' depend on the temperature. By invoking some exact results from statistical mechanics we offer an alternative method to compute shear moduli using Molecular Dynamics simulations, and compare those to the Monte-Carlo method. The final conclusion is that these systems are not "viscous fluids" in the usual sense, as their actual time-dependence concatenates solid-like materials with varying local shear moduli.