CRITERIA FOR THE EVALUATION OF HYPOTHETICAL ZEOLITE FRAMEWORKS

Inspection of zeolite framework shows that i) largest voids are usually found in positions of highest symmetry of the space group, and ii) two 4-rings with a common edge prefer the "cis" conformation with nearly planar rings and a maximum of T-T-T-angles near 109° over the "trans" conformation. The observations are explained by ionic and covalent bond tendencies. Analogies with calculated clusters of point charges are drawn. The observations can help to generate and to select probable theoretical nets. Suggested nets for NaP and VPI-5 appear to be uncommon. © 1990 Butterworth-Heinemann.