Gramm Fabian, Baerlocher Christian, McCusker Lynne B, Warrender Stewart J, Wright Paul A, Han Bada, Hong Suk Bong, Liu Zheng, Ohsuna Tetsu, Terasaki Osamu
Laboratory of Crystallography, ETH Zurich, 8093 Zurich, Switzerland.
Nature. 2006 Nov 2;444(7115):79-81. doi: 10.1038/nature05200.
Many industrially important materials, ranging from ceramics to catalysts to pharmaceuticals, are polycrystalline and cannot be grown as single crystals. This means that non-conventional methods of structure analysis must be applied to obtain the structural information that is fundamental to the understanding of the properties of these materials. Electron microscopy might appear to be a natural approach, but only relatively simple structures have been solved by this route. Powder diffraction is another obvious option, but the overlap of reflections with similar diffraction angles causes an ambiguity in the relative intensities of those reflections. Various ways of overcoming or circumventing this problem have been developed, and several of these involve incorporating chemical information into the structure determination process. For complex zeolite structures, the FOCUS algorithm has proved to be effective. Because it operates in both real and reciprocal space, phase information obtained from high-resolution transmission electron microscopy images can be incorporated directly into this algorithm in a simple way. Here we show that by doing so, the complexity limit can be extended much further. The power of this approach has been demonstrated with the solution of the structure of the zeolite TNU-9 (|H9.3|[Al9.3Si182.7O384]; ref. 10) with 24 topologically distinct (Si,Al) atoms and 52 such O atoms. For comparison, ITQ-22 (ref. 11), the most complex zeolite known to date, has 16 topologically distinct (Si,Ge) atoms.
许多具有重要工业价值的材料，从陶瓷到催化剂再到药品，都是多晶的，无法生长成单晶。这意味着必须应用非常规的结构分析方法来获取对于理解这些材料性质至关重要的结构信息。电子显微镜似乎是一种自然的方法，但通过这种途径仅解决了相对简单的结构。粉末衍射是另一个明显的选择，但具有相似衍射角的反射峰重叠会导致这些反射峰相对强度的模糊性。已经开发出各种克服或规避此问题的方法，其中一些方法涉及将化学信息纳入结构确定过程。对于复杂的沸石结构，FOCUS算法已被证明是有效的。由于它在实空间和倒易空间中都能运行，从高分辨率透射电子显微镜图像获得的相位信息可以以简单的方式直接纳入该算法。在这里我们表明，通过这样做，复杂度极限可以进一步大大扩展。通过解析具有24个拓扑不同的（硅，铝）原子和52个此类氧原子的沸石TNU-9（|H9.3|[Al9.3Si182.7O384]；参考文献10）的结构，证明了这种方法的强大功能。作为比较，ITQ-22（参考文献11）是迄今为止已知的最复杂的沸石，具有16个拓扑不同的（硅，锗）原子。
