We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of rela...

Inorganic glasses, glass-forming liquids and amorphizing solids

Publisher Summary This chapter explores that the influence of boron chemistry on various areas of research in inorganic, organic, and theoretical chemistry is well documented. In fact, many models currently employed to describe chemical bonding in general can be traced to attempts to understand bonding in boranes. The confirmation of many theoretical predictions in boron chemistry relies on direct and indirect structural information provided by various physical methods that fortunately became available almost at the same rate as that with which the interest in boron compounds was growing. It discusses that developments in boron chemistry have been greatly accelerated by nuclear magnetic resonance (NMR). 11 B NMR has been at the centre of interest from the beginning accompanied by routine 1 H NMR measurements: and occasional 14 N, 19 F and 31 P NMR work. The availability of “multinuclear” facilities for PFT NMR spectrometers stimulates the measurement of the NMR spectra of other nuclei, like 29 Si, l19 Sn or other metals, to obtain additional information. The chapter not only summarizes the experimental facts required for obtaining the maximum information from NMR studies on boron compounds but also attempts to incorporate new NMR parameters into the known data set.

Nuclear Magnetic Resonance Spectroscopy of Boron Compounds Containing Two-, Three- and Four-Coordinate Boron

Preparation schemes for high-purity vitreous B{sub 2}S{sub 3} (v-B{sub 2}S{sub 3}) with a S:B ratio of 1.478 {plus minus} 0.032 are described. Preparation schemes reported in the literature are shown by very sensitive FT-IR measurements to yield v-B{sub 2}S{sub 3} with significant oxygen contamination. Through extreme care taken in carbonizing silica reaction tubes and through the use of very high purity starting materials, oxygen contamination of less than 1% has been achieved. The IR spectrum for very pure v- B{sub 2}S{sub 3} contains only two absorption bands.

Preparation of High-Purity Vitreous B2S3

Preparation, crystal structure and 7Li NMR of Li6+2x[B10S18]Sx(x≈)

Publisher Summary This chapter reviews some of the developments in 11 B nuclear magnetic resonance (NMR) spectroscopy. Major use of 11 B has been archival—that is, use for routine characterization of new compounds—although considerable efforts to elucidate correlations between structure and NMR parameters continue. The chapterdiscusses that availability of high-field spectrometers with multinuclear capability as well as software for sophisticated data manipulation is increasingly common, and, with these instruments, lack of chemical-shift dispersion in the face of relatively large linewidths presents much less of a problem than when complex polyboron compounds are to be characterized. Coupled with this, potent separation techniques—exemplified by thin-layer, high-pressure, and ion-exchange chromatography—are able to unravel complex mixtures and make pure compounds available for study. Use of X-ray crystallographic facilities with which to structurally characterize compounds whose spectra are reported is today almost a routine. The chapter also discusses that NMR spectra of solids are becoming increasingly easy to obtain, and application of this technique to solids is, albeit slowly, gaining well-deserved attention. A principle application has been to the study of amorphous solids and materials lacking long-range order.

Werner Mueller-Warmuth

Papers

Solid-state boron-11 NMR studies on boron-chalcogenide systems

Solid‐State NMR Structural Studies of the Ternary Molybdenum Cluster Chalcogenides CdxMo6Se8 (x = 1, 2).