The Origin of Deformation Induced Topological Anisotropy in Silica Glass

TL;DR

This paper uncovers how mechanical deformation induces topological anisotropy in silica glass at the atomic level, revealing the microscopic mechanisms and how loading modes control the orientation of SiO4 tetrahedra, impacting material properties.

Contribution

It introduces novel analysis methods to understand the atomic-scale origin of anisotropy in silica glass caused by mechanical loads, linking deformation protocols to structural changes.

Findings

Anisotropy stems from preferred SiO4 tetrahedra orientation.

Loading mode influences the anisotropic structure.

Structural anisotropy affects material properties.

Abstract

Oxide glasses with a network structure are omnipresent in daily life. Often, they are regarded as isotropic materials; however, structural anisotropy can be induced through processing in mechanical fields and leads to unique materials properties. Unfortunately, due to the lack of local, atomic-scale analysis methods, the microscopic mechanisms leading to anisotropy remained elusive. Using novel analysis methods on glasses generated by molecular dynamics simulations, this paper provides a microscopic understanding of topological anisotropy in silica (SiO$_2$) glass under mechanical loads. The anisotropy observed in silica glass originates from a preferred orientation of SiO$_4$ tetrahedra at both short- and medium-range levels that can be controlled via the mode of mechanical loading. The findings elucidate the relation between the deformation protocol and the resulting anisotropic structure of the silica network (involving both persistent and transient effects), and thus provide important insight for the design of oxide glasses with tailored materials properties.