Electron crystallography of zeolites. 1. Projected crystal structures of ZSM-5 and ZSM-11

Abstract

Abstract The prospect of carrying out quantitative crystal structure analyses by direct methods with electron diffraction intensity data from zeolites is evaluated for two related materials: ZSM-5 and ZSM-11. The stacked plate-like arrays of ZSM-5 induce intensity perturbations from secondary electron scattering; nevertheless, the T-site positions can be found by direct methods. Intensity data from smaller ZSM-11 microcrystals are more favorable for ab initio analysis so that some oxygen positions are found during Fourier refinement. For intergrowths of one zeolite in the other, the nature of the inclusions has been found to depend on the dominant species. If ZSM-5 is dominant, the apparent ZSM-11 inclusions (assuming a preferred platy orientation) could be rather large, whereas if ZSM-11 is dominant, the ZSM-5 inclusions extend over only 3 or 4 unit cells.