Harding M M
J Synchrotron Radiat. 1996 Nov 1;3(Pt 6):250-9. doi: 10.1107/S090904959600862X.
An account is given of experiences in recording diffraction data with synchrotron radiation to determine structures for very small crystals, too small for use with conventional X-ray sources and diffractometers. The effect of crystal composition as well as size on the relative intensity of diffraction patterns of different crystals is noted. Crystal mounting is briefly described. Experimental methods are outlined including detectors and other instrumentation, and a range of examples is given; these include the use of both monochromatic area-detector systems for intensity measurement and of the white-beam Laue method. Choice of the shortest wavelength available with adequate intensity is recommended. The examples include organic, organometallic and aluminophosphate compounds; in all cases structure determination was important in relation to chemical research projects - they were not chosen as ;test' crystals. Comparison is made of the quality of the structure refinements achieved with those from synchrotron radiation powder diffraction - the alternative method when good-sized crystals are not available. Commonly it is found that when good-quality large crystals of a substance cannot be grown, the small crystals are poor in quality with substantial mosaic spread; the relationship between mosaic spread, structure, morphology and crystal growth is explored.
本文介绍了利用同步辐射记录衍射数据以确定非常小的晶体结构的经验，这些晶体太小，无法使用传统X射线源和衍射仪。文中指出了晶体组成和尺寸对不同晶体衍射图案相对强度的影响。简要描述了晶体安装方法。概述了实验方法，包括探测器和其他仪器，并给出了一系列示例；这些示例包括使用单色面探测器系统进行强度测量以及白光劳厄法。建议选择具有足够强度的最短波长。示例包括有机、有机金属和磷酸铝化合物；在所有情况下，结构测定对于化学研究项目都很重要——它们并非作为“测试”晶体被选择。文中将同步辐射粉末衍射所获得的结构精修质量与利用同步辐射进行结构精修的质量进行了比较——当无法获得尺寸合适的晶体时，粉末衍射是另一种方法。通常发现，当无法生长出高质量的大晶体时，小晶体质量较差，存在大量镶嵌展宽；文中探讨了镶嵌展宽、结构、形态与晶体生长之间的关系。
