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For topological considerations, an atomic network is treated as if the observer is “chemically blind.” In other words, the network is considered simply as a combination of vertices and edges disregarding the nature of the atoms occupying the vertices. Thus, topology refers only to how the nodes are interconnected in a network.

Local (or short‐range) topology at the ith vertex is described by the number (r_i) of edges shared by that vertex (i.e. the vertex coordination number). A vertex having r_i = 1 is called non‐bridging or dangling. Vertices with r_i > 1 are called bridging (or network‐forming). When r_i is the same for all vertices, the network is called regular. Otherwise, it is irregular. For an irregular network, the average vertex coordination number, r, also called the connectivity, provides a measure of its short‐range topology. Note that, in chemically ordered networks, r is related to the two coordination numbers V and C by

(1)

The intermediate‐range topology of a network is characterized by its ring‐size distribution so that it, for instance, depends on whether neighboring structural units share edges or corners. By definition, noncrystalline networks have no long‐range topological order. For this reason, they are termed topologically disordered (TD) networks [4].