PerspectiveAmorphous Materials

Glimpsing glass structure under pressure

Science  29 Aug 2014:
Vol. 345, Issue 6200, pp. 998-999
DOI: 10.1126/science.1258785

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Summary

Archaeologists suggest that the earliest known use of glass, natural obsidian, dates to the Stone Age, with extensive “modern” utilization as early as ∼12,500 BCE (1). The first historical appearance of synthetic glass is around ∼5000 BCE, where it was used as a glaze on clay and stone beads (2). Today, glass has broad uses in technology, architecture, packaging, and art. Throughout the technological (and artistic) advances in inorganic glasses, temperature has remained the single most important variable, controlling glass formation and playing a critical role in the short-range atomic structure of these disordered solids. On page 1027 of this issue, Edwards et al. (3) present findings on glass structure where pressure is the extrinsic variable. Using a novel nuclear magnetic resonance (NMR) methodology, they measured the boron-11 NMR spectrum of a borosilicate glass as a function of pressure in situ, in contrast to the more common postcompression analyses of glass. Their findings, augmented with ab initio calculations, demonstrate deformation of planar BO3 triangles, a key feature in boron-containing glasses, that leads to their eventual conversion to fourfold coordinated boron.