Diffraction by powders

However, this does not mean that the technique is imimportant. In fact, the opposite is true. There are far more powder diffraction instruments than single-crystal diffractometers and the technique is widely used, particularly in industry. Compounds or mixtures can be identified by comparing their diffraction patterns, used as fingerprints, with databases of known compounds. Note that it is a straightforward process to calculate a powder diffractogram for any structure obtained by single-crystal diffraction methods. Industrial applications are often sensitive to phase purity and polymorph issues, and these can be quickly assessed by powder diffraction. It is even possible to use it for quantitative phase analysis, and it can be applied to follow reactions in situ by following the disappearance and appearance of phases. 

It is not only X-rays that can be used for powder studies. Neutron powder diffraction is also widely applicable, but of course this is a much more expensive way to elucidate structures. It can often come to the rescue when large single crystals for neutron diffraction work cannot be grown. We cover this topic in more detail in the case history describing temperature and pressme-driven proton transfer in an adduct formed between squaric acid and bipyridine (Section 12.14). 

Finally, we note that powder diffraction can also be apphed as a surface technique, which opens a very wide field of interest, but one that is beyond the scope of this book. 

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