Local Deformation of Glasses Is Mediated by Rigidity Fluctuation and Granularity

Abstract

Microscopic deformation processes lie at the origin of defect formation on glass surfaces, thus determining the material’s resistance to scratching and mechanical failure. While the macroscopic strength of most glasses is not directly depending on material composition, local deformation and flaw initiation are strongly affected by chemistry and atomic arrangement. Aside empirical insight, however, the structural origin of the fundamental deformation modes remains largely unknown. Experimental methods which probe parameters on short or intermediate length-scale such as atom-atom or super-structural correlations are typically applied in the absence of alternatives. Drawing on recent experimental advances, we now probe spatial variations in the low-frequency vibrational density of states which result from sharp contact deformation of vitreous silica. From direct observation of deformation-induced variations on the characteristic length-scale of molecular heterogeneity, we argue that rigidity fluctuation on the scale of a few nanometers governs the deformation process of inorganic glasses.