Transient Nature of Fast Relaxation in Metallic Glass

TL;DR

This study uses molecular dynamics simulations to investigate the origin of nearly constant loss (NCL) in metallic glasses, revealing that NCL arises from transient atomic groups that are spatially distributed and not defect-like.

Contribution

It identifies the atomic groups responsible for NCL as fully transient and spatially distributed, challenging previous defect-based explanations.

Findings

NCL is due to transient atomic groups that become normal over picoseconds.

These groups are spatially distributed and lack defect-like features.

The work provides atomic-level insight into low-temperature relaxation phenomena.

Abstract

Metallic glasses exhibit fast mechanical relaxations at temperatures well below the glass transition, one of which shows little variation with temperature known as nearly constant loss (NCL). Despite the important implications of this phenomenon to in aging and deformation, the origin of the relaxation is unclear. Through molecular dynamics simulations of a model metallic glass, Cu_64.5Zr_35.5, we implement dynamic mechanical analysis with system stress decomposed into atomic-level stresses to identify the group of atoms responsible for NCL. This work demonstrates that NCL relaxation is due to fully transient groups of atoms that become normal over picosecond timescales. They are spatially distributed throughout the glass and have no outstanding features, rather than defect-like as previously reported.