Topology of anisotropic glasses from persistent homology analysis

Abstract

Glasses are typically isotropic, but permanent or transient anisotropy can be induced by tensile strain. We use persistent homology (PH) analysis to explore the topological effects of such anisotropy in SiO2Na2O glass ensembles with variable alkali concentration as a function of frozen-in anisotropic strain. Statistical information was extracted on ring (H1) and cavity (H2) features, whereby anisotropic stretching was found to induce strong variations in the ring topology of the –O-Si-O- backbone, but only minor changes in the overall cavity statistics or in the Na distribution (the Na distribution was found to be governed by H2 persistence). Tensile fracture led to total recovery of network topology relative to the pristine (isotropic) glass. In revealing such reactions, PH and persistence similarity analysis may help to differentiate purely entropic orientation and irreversible structural alterations leading to glass anisotropy.