Thermal processing and enthalpy storage of an amorphous solid: a molecular dynamics study

TL;DR

This study uses extensive molecular dynamics simulations to explore how an amorphous solid stores and releases enthalpy during thermal processing, revealing the dominant role of enthalpy in structural relaxation.

Contribution

It provides new insights into the thermally activated relaxation mechanisms in amorphous solids, emphasizing the importance of enthalpy over energy, supported by long-scale simulations.

Findings

Enthalpy changes are comparable to experimental observations.

Structural relaxation correlates with internal stress homogenization.

Local structural excitations increase with temperature.

Abstract

Using very long molecular dynamics simulation runs, temperature protocols spanning up to five orders of magnitude in time-scales are performed to investigate thermally activated structural relaxation in a model amorphous solid. The simulations demonstrate significant local structural excitations as a function of increasing temperature and show that enthalpy rather than energy is primarily responsible for relaxation. The observed enthalpy changes are of the order seen in experiment, and can be correlated with the level of internal hydrostatic stress homogenization and icosahedral content within the solid.