Abstract
Microscopic deformation processes determine defect formation on glass surfaces and, thus, the material's resistance to mechanical failure. While the macroscopic strength of most glasses is not directly dependent on material composition, local deformation and flaw initiation are strongly affected by chemistry and atomic arrangement. Aside from empirical insight, however, the structural origin of the fundamental deformation modes remains largely unknown. Experimental methods that probe parameters on short or intermediate length‐scale such as atom–atom or superstructural correlations are typically applied in the absence of alternatives. Drawing on recent experimental advances, spatially resolved Raman spectroscopy is now used in the THz‐gap for mapping local changes in the low‐frequency vibrational density of states. From direct observation of deformation‐induced variations on the characteristic length‐scale of molecular heterogeneity, it is revealed that rigidity fluctuation mediates the deformation process of inorganic glasses. Molecular field approximations, which are based solely on the observation of short‐range (interatomic) interactions, fail in the prediction of mechanical behavior. Instead, glasses appear to respond to local mechanical contact in a way that is similar to that of granular media with high intergranular cohesion.
Highlights
Microscopic deformation processes determine defect formation on glass on haptic interaction and, are prone to surface damage, for example, touch surfaces and, the material’s resistance to mechanical failure
The mechanical behavior of glasses and their surfaces has Focusing on vitreous silica as an archetypal model, Perriot become a subject of widespread interest.[1]
We considered the topological origin of microscopic deformation processes on glass surfaces in sharp contact situations
Summary
In order to judge the individual contributions of densification and shear to the deformationinduced variation of Boson Peak frequency, low-frequency Raman mappings are compared before (Figure 2a) and after annealing (Figure 2b, annealed for 24 h at 0.9 × Tg). This assumes that structural compaction fully relaxes during annealing, whereas shear deformation does not. While the principal Raman signature remains unchanged before and after annealing, during heat treatment, stress relaxation is accompanied by structural relaxation[56] and the indentation-induced structural change recovers to a large extent This confirms previous observations that indentation deformation of silica glass occurs primarily through structural compaction. We further notice that the maximum densification observed here is somewhat smaller than the expected saturation value of about 21% which has been reported for vitreous silica.[32]
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