Predicting Complex Relaxation Processes in Metallic Glass

TL;DR

This paper combines molecular dynamics simulations and experiments to predict and verify complex relaxation behaviors in a metallic glass, revealing microscopic origins and advancing understanding in glass physics.

Contribution

It introduces a predictive approach for complex relaxation processes in metallic glasses using simulations verified by experiments, highlighting microscopic mechanisms.

Findings

Identification of primary, secondary, and anomalous relaxation processes.

Correlation of relaxation behaviors with atomic rearrangements and decoupling.

Verification of predictions through experimental data.

Abstract

Relaxation processes significantly influence the properties of glass materials. However, understanding their specific origins is difficult, even more challenging is to forecast them theoretically. In this study, using microseconds molecular dynamics simulations together with an accurate many-body interaction potential, we predict that an Al$_{\text{90}}$Sm$_{\text{10}}$ metallic glass would have complex relaxation behaviors: In addition to the main ($\alpha$) relaxation, the glass (i) shows a pronounced secondary ($\beta$) relaxation at cryogenic temperatures and (ii) exhibits an anomalous relaxation process ($\alpha_2$) accompanying $\alpha$ relaxation. Both of the predictions are verified by experiments. Computational simulations reveal the microscopic origins of relaxation processes: while the pronounced $\beta$ relaxation is attributed to the abundance of string-like cooperative atomic rearrangements, the anomalous $\alpha_2$ process is found to correlate with the decoupling of the faster motions of Al with slower Sm atoms. The combination of simulations and experiments represents a first glimpse of what may become a predictive routine and integral step for glass physics.