The structure and dynamics of alkali silicate liquids: A view from NMR spectroscopy

Understanding and predicting the macroscopic properties of silicate liquids require information on both structure and dynamics. Studies of glass structure provide a convenient starting point, but only represent the liquid at the rather low temperature of transition from glass to liquid. In situ high-T studies, as well as work on glasses with varying fictive temperature, can provide more information on structural changes with T and on dynamical mechanisms. Here we discuss the application of NMR spectroscopy to both kinds of approaches. We present results, primarily from our laboratory, on anionic species distributions, on silicon and oxygen site exchange in liquids and its relationship to viscosity, and on the quantification of the abundances of five- and six-coordinated Si in high-pressure and 1-bar-pressure glass samples.