Solving complex open-framework structures from X-ray powder diffraction by direct-space methods using composite building units

J. Appl. Cryst. (2013). 46, 1094-1104 (http://doi.org/nss)

The open-framework structure of germanate SU-66 solved from X-ray powder diffraction using the software FOX. The framework was built by Ge₁₀(O,OH)₂₇ (Ge₁₀) clusters, each consisting of six GeO₄ tetrahedra (in green) and four GeO₆ octahedra (in red). Additional GeO₄ tetrahedra not belonging to any Ge₁₀ clusters are in blue.

Solving structures of complex open-frameworks from powder diffraction is often challenging because of peak overlapping. We show that if the building units can be identified, open-framework structures can be solved ab initio from X-ray powder diffraction data using the parallel tempering algorithm implemented in the software FOX. Infrared spectroscopy was used for the first time to identify the building unit in a novel germanate denoted SU-66. The structure of SU-66, with 55 unique atoms in the asymmetric unit, was solved from in-house X-ray powder diffraction data.