Non-affine atomic rearrangement of glasses through stress-induced structural anisotropy

The atomic-scale structural rearrangement of glasses on applied stress is central to the understanding of their macroscopic mechanical properties and behaviour. However, experimentally resolving the atomic-scale structural changes of a deformed glass remains challenging due to the disordered nature of the glass structure. Conventional structural analyses such as X-ray diffraction are based on the assumption of structural isotropy and hence cannot discern the subtle atomic-scale structural rearrangement induced by deformation. Here we show that structural anisotropy correlates with non-affine atomic displacements-meaning those that do not preserve parallel lines in the atomic structure-in various types of glass. This serves as an approach for identifying the atomic-scale non-affine deformation in glasses. We also uncover the atomic-level mechanism responsible for plastic flow, which differs between metallic glasses and covalent glasses. The non-affine structural rearrangements in metallic glasses are mediated through the stretching or contraction of atomic bonds. The non-affinity of covalent glasses that occurs in a less localized manner is mediated through the rotation of atomic bonds or chains without changing the bond length. These findings provide key ingredients for exploring the atomic-scale process governing the macroscopic deformation of amorphous solids. Resolving the structural changes of a deformed glass on the atomic scale is challenging due to its disordered nature. Now, high-energy diffraction measurements show that non-line-preserving atomic displacements in glasses correlate with structural anisotropy.

Automated summary

The atomic-scale structural rearrangement of glasses under stress is important for understanding their macroscopic mechanical properties. However, it is challenging to experimentally resolve the atomic-scale structural changes of a deformed glass due to its disordered nature. This study shows that structural anisotropy is correlated with non-affine atomic displacements in glasses, providing an approach to identify atomic-scale non-affine deformation. The study also reveals the atomic-level mechanism responsible for plastic flow, which differs between metallic glasses and covalent glasses.