Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 181

For crystalline materials, the structure is formed from exact repetitions of a huge number of identical (or almost identical) unit cells. Thus, for the most part, a structure solution simply requires the determination of the positions of the relatively very small number of atoms in the unit cell. The methods of crystallography are immensely powerful so that diffraction methods are pre‐eminent in this respect.

Contrastingly, glass is by definition noncrystalline. To determine the statistical distributions of its structural parameters, such as bond length, bond angle, ring size, and so on, structural studies have few of the advantages enjoyed by crystallographers for crystals. Because the amount of information that can be obtained from a single experiment on a glass is small, structural studies are much slower to proceed for glasses than for crystals, and researchers have to fight for each grain of information. In view of this challenge to obtain reliable information, in past decades it has been necessary for researchers to become expert in a particular experimental technique to achieve reliable progress. Nowadays, however, not only are most experimental probes of glass structure well established but their capabilities are steadily being improved as well. It is thus becoming possible to use a number of experimental methods well, so that significant progress is likely to be made by the increasing application of multi‐technique methods to the same set of glass samples; for instance, a combination of ND, XRD, NMR, and Raman scattering can reveal a more complete description of the structure of a glass. With the steady improvement of experimental methods and their interpretation, and such a growing use of multiple techniques, it is likely that gradually more complex glasses will be studied with a growing resolution, and that modeling will have in parallel an increasingly significant role in improving our understanding of glass structure.