Zachariasen Random Network Theory

Zachariasen could successfully explain why certain CNs are favoured for glass formation. Zachariasen random network theory formed the basis of glass formation. During his studies, he observed that the silicate crystals have a tetrahedral network and readily form glass. These tetrahedral networks are symmetrical, non-periodic, and connected with each other at the comers. This leads to the 3-D network extended over aU directions with the isotropic property attributed to the amorphous nature of glasses. He elucidated the following points during his studies. 

These postulates given by Zachariasen are to be satisfied by a melt for glass formation. 

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The first theory of the structure of glass to become widely accepted was that of Zachariasen (1932), called the random network theory [now commonly referred to as the continuous random network (CRN) theory]. This arose... 

The strnctnral polyhedra are those that we have already been using triangles, tetrahedra, and octahedra. Zachariasen s rnles, as supported and modified by Warren, came to be known as the random network theory and, despite its limitations, is still widely nsed. 

A number of other statements by Zachariasen have become the basis for the models for glass structures termed the Random Network Theory. These ideas will be discussed later under the topic of glass structure. It is interesting to note, however, that the term random network does not occur in the original work of Zachariasen, who referred to the glass structure as a vitreous network . Furthermore, Zachariasen specifically states that the vitreous network is not entirely random due to the restriction of a minimum value for the internuclear distances. As a result, all internuclear distances are not equally probable, and X-ray patterns of the type observed for glasses are a natural consequence of the vitreous network. 

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