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Angew. Chem.最新文章：晶体结构预测
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Every year thousands of new crystal structures are determined and many of these are molecular crystal structures. However, while an enormous amount of structural data is available, it has proven rather difficult to predict molecular crystal structures given only the structural formula. As with all chemical transformations, a change in energy is the driving force underlying the formation of any crystal, and both kinetic as well as thermodynamic contributions are important. Molecular crystals are held together primarily by dispersion forces which are comparatively weak and notoriously difficult to calculate accurately. In 1994 in a seminal paper entitled “Are Crystal Structures Predictable?” Gavezotti stated a clear “No” and pointed out that the small energy differences between hypothetical crystal structures are the limiting factor for successful crystal structure predictions.[1] Since then, this dogma has been challenged numerous times, most prominently by a series of blind tests organized by the Cambridge Crystallographic Data Centre (CCDC). So far a total of five such blind tests have been organized and the crystal structure predictions have become more accurate, despite increased challenges posed by the organizers.[2] For these tests a small number of organic compounds are selected with hitherto unpublished crystal structures. The participants are asked to propose three candidate crystal structures for each compound which are matched against the secret experimental crystal structures. For the latest series, which was concluded in 2010, the results have been submitted and analyzed but not yet published. This study included six categories of increasing complexity and, for the first time, it also included systems with known polymorphism and more flexible molecules |
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