Single-crystal neutron diffraction, zeolite

The five years since last considering specifically recent developments in X-ray and neutron diffraction methods for zeolites [1] have witnessed substantial progress. Some techniques, such as high resolution powder X-ray diffraction using synchrotron X-rays, have blossomed from earliest demonstrations of feasibility to widespread and productive application. Others, such as neutron powder diffraction, have shown steady progress. For still others, notably microcrystal diffraction, a variety of circumstances have contributed to extended gestation periods. Additionally, opportunities scarcely considered earlier (such as single crystal Laue diffraction, and certain developments in computer simulations that complement diffraction work) now command broad attention and warrant the commitment of substantial further investment. 

Newsam reviewed the various neutron and X-ray diffraction techniques used for zeolite characterization. A particular problem of zeolites is that the crystals are very small, usually less than 5 yum on an edge. This is about three orders of smaller in volume than suitable for single crystal diffraction work. Stacking disorders are common but sometimes very subtle. For example the AABAAC six-ring sequence of erionite differs only in the orientation of every sixth plane from the AABAAB sequence of offretite. 

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