Atomic-scale Deformation Process of Glasses Unveiled by Stress-induced Structural Anisotropy

TL;DR

This study reveals that structural anisotropy, detectable via high-energy X-ray diffraction, is a universal marker of atomic-scale deformation in various glasses, elucidating different plastic flow mechanisms.

Contribution

It demonstrates the emergence of structural anisotropy as a universal hallmark in deformed glasses and uncovers distinct atomic-level deformation mechanisms for metallic and covalent glasses.

Findings

Structural anisotropy correlates with local atomic displacements.

Different deformation mechanisms in metallic vs. covalent glasses.

Atomic rearrangements involve bond formation/breaking or rotation.

Abstract

Experimentally resolving atomic-scale structural changes of a deformed glass remains challenging owing to the disordered nature of glass structure. Here, we show that the structural anisotropy emerges as a general hallmark for different types of glasses (metallic glasses, oxide glass, amorphous selenium, and polymer glass) after thermo-mechanical deformation, and it is highly correlates with local nonaffine atomic displacements detected by the high-energy X-ray diffraction technique. By analyzing the anisotropic pair density function, we unveil the atomic-level mechanism responsible for the plastic flow, which notably differs between metallic glasses and covalent glasses. The structural rearrangements in metallic glasses are mediated through cutting and formation of atomic bonds, which occurs in some localized inelastic regions embedded in elastic matrix, whereas that of covalent glasses is mediated through the rotation of atomic bonds or chains without bond length change, which occurs in a less localized manner.