TABLE OF CONTENTS A complete structural model for any glass must contain a number of elements, as indicated in Table 5.2. A number of these elements will be discussed in some detail before proceeding to a discussion of structural models of a number of common glasses.
| REQUIRED ELEMENTS FOR ANY COMPLETE STRUCTURAL MODEL FOR GLASSES |
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The coordination numbers of all cations which occupy sites in the vitreous network, i.e., the building blocks which constitute the network, provide the most basic element of any model for glass structures. Since these building blocks are usually well defined structures such as tetrahedra or triangles, they exhibit order at the level of several associated atoms or ions. Since this order only extends over a very short distance, it is termed short range order.
It follows that the starting point for any model for the structure of a vitreous material must lie in a determination of the coordination unit for the high field strength cations, which serve as the network forming cations in the material. Traditionally, we estimate the possible coordination number of each cation using the radius ratio, or by...
