| Abstract
| - Since the last major study of silicate crystal structures, many new pure silica zeolite-type frameworks have been discovered. These materials have many interesting properties that are dependent on their structure. We have brought together and analyzed the structures in 35 well-defined frameworks to see how they differ from one another depending on the synthetic route, template, calcination, and composition, and how they differ from the dense silicate phases previously examined. The grand mean values of the Si−O bond distance and the O−Si−O angle are found to be 1.594 Å and 109.5°, respectively. The variation and flexibility of the Si−O−Si bond from 133.6 to 180° is discussed, as is the role of fluoride in influencing the O−Si−O bond angles in phases prepared using hydrofluoric acid and ammonium fluoride as mineralizers.
- We have analyzed bond lengths and angles in the crystal structures of 35 pure silica zeolites. The very flexible Si−O−Si angle varies from 125 to 180°. The role of fluoride in distorting the SiO4 tetrahedra is discussed, as are the interesting thermal properties of some of the materials.
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