Zachariasen’s model

This parabolic trend can be surmised from Eq. (15), where the occupation numbers n are proportional to Z (the parabola should have a minimum at Cm, i.e. or the half-filling of the 5f shell). The same parabolic trend exists in d-transition metals, and is explained in Friedel s model in a similar way. This fact had seemed to early theorists (see, in Chap. A, the discussion of Zachariasen s model) to suggest that the actinides were 6 d-transition metals. In reality, it means that the light actinides are 5f-transition metals, with the 5 f wavefunctions playing the role of d-wavefunc-tions. 

To summarize, Zachariasen s model has dominated glass science for several decades and is still extremely useful. However, diffraction methods do not actually provide definite proof for such a model they can only confirm that the results do not contradict this hypothesis. Remember also that the model was developed specifically for oxide glasses and is not necessarily applicable to other types of glasses. 

Figure 7.10. (a) Zachariasen s two-dimensional model of an AiOj glass, after Zachariasen (1932). (b) Two-dimensional representation of a sodium silicate glass,... 

Figure 1.43 Zachariasen s random network model for AjBj glass.

The simplest model of glass structure, Zachariasen s continuous random network model, represents glasses as being formed by random... 

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