Experimental methods in X-ray and neutron crystallography

This chapter discusses the experimental methods used to study the diffraction of X-rays and neutrons by crystalline materials. Although, as seen in appendix 3.B.5, electrons are also diffracted by crystals, we will not treat electron diffraction in any detail but the topic is partially covered in Chapter 10.9. We start by describing how X-rays and neutrons are produced and how one can define the beam of radiation that will interact with the crystalline sample. The specimens that will receive our attention are single crystals and polycrystalline materials, the latter being ensembles of a large number of small single crystals or aggregates of small coherently scattering crystalline domains. We proceed by discussing in separate sections the methods used to record the diffraction pattern and to quantitatively measure the intensity of radiation scattered by these two types of specimen. The ultimate goal of extracting structure factor amplitudes from diffracted intensities requires the application of a series of correction factors. This process, called data reduction, is discussed in the final section of the chapter