Although methodology for determining the crystal structures of polycrystalline materials has developed rapidly in recent years, zeolites continue to offer a challenge to these methods. The zeolite-specific program Focus, which can be viewed as an intelligent automated modelbuilding procedure, has been particular successful, but it has its limits. An alternative approach, based on the single-crystal charge-flipping algorithm and adapted to accommodate powder diffraction data (pCF), was also shown to work well in tests on known zeolite structures. To address the more complex structures (e.g. with more than 12 topologically distinct T-atoms), however, more information is needed. High-resolution transmission electron microscopy (HRTEM) images are an excellent source of such information. By combining powder diffraction and electron microscopy data in a single program, the structure of TNU-9 has been solved using Focus and the structure of IM-5 using pCF. Both zeolite structures have 24 topologically distinct T-atoms in the asymmetric unit. Details of the methods and of the structure solutions are given.
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