Observation of the transition state for pressure-induced BO 3 → BO 4 conversion in glass

Catching changing boron coordination Laboratory glassware and kitchen cookware alike are made of glass that contains different cations, including boron, sodium, and aluminum. Properties of glass depend on the number and location of oxygen atoms surrounding each cation. Edwards et al. combine nuclear magnetic resonance measurements with theoretical calculations to understand structural transformations in borosilicate glass (see the Perspective by Youngman). Boron atoms in planar threefold coordination move out of plane with increasing pressure to form trigonal pyramids. Identification of this type of transition state connects structural evolution with stress-induced processes in amorphous materials. In borosilicate glass, the transition leads to the formation of tetrahedral fourfold-coordinated boron that tunes glass properties for use in numerous applications. Science , this issue p. 1027 ; see also p. 998