McCusker Lynne B, Baerlocher Christian
Laboratory of Crystallography, ETH Zurich, CH-8093, Zurich, Switzerland.
Chem Commun (Camb). 2009 Mar 28(12):1439-51. doi: 10.1039/b821716e. Epub 2009 Feb 20.
High-resolution X-ray powder diffraction and electron microscopy techniques yield remarkably complementary information for crystal structure determination. By combining the two types of data, structures of polycrystalline materials that resist solution by more conventional methods can be tackled. In particular, crystallographic phase information extracted either from high-resolution transmission electron microscopy (HRTEM) images or from precession electron diffraction (PED) data has proven to be extremely useful in such cases. PED data can also be used to identify weak reflections in the diffraction pattern, and this information, in turn, can be exploited to improve the partitioning of the intensities of reflections that overlap in the powder diffraction pattern. The dual-space (diffraction and real space) structure determination programs Focus and pCF have been shown to be especially well-suited for combining the two different types of data. The power of this approach is illustrated with the details of the solutions of the structures of TNU-9, IM-5 and SSZ-74, the three most complex zeolite framework structures known.
高分辨率X射线粉末衍射和电子显微镜技术在晶体结构测定方面能产生显著互补的信息。通过结合这两类数据，可以解决用更传统方法难以解析的多晶材料结构问题。特别是，从高分辨率透射电子显微镜（HRTEM）图像或进动电子衍射（PED）数据中提取的晶体学相信息在这类情况下已被证明极为有用。PED数据还可用于识别衍射图谱中的弱反射，反过来，这些信息可用于改善粉末衍射图谱中重叠反射强度的分配。双空间（衍射和实空间）结构测定程序Focus和pCF已被证明特别适合于结合这两种不同类型的数据。通过已知的三种最复杂的沸石骨架结构TNU-9、IM-5和SSZ-74的结构解析细节说明了这种方法的强大之处。
