5. Chemical Crystallography

Abstract

This chapter discusses chemical crystallography. The chapter begins with a discussion of the reasons for using neutron diffraction for certain problems and a description of the data-collection equipment and procedures at steady-state reactor and pulsed spallation neutron sources. This is followed by an outline of the steps required for determining a crystal structure. Single-crystal neutron diffraction provides unique insight into the structure and bonding of molecules, which is often directly relevant to the chemistry of the molecules. A description of the steps required in collecting data, reducing the data to structure factor amplitudes, obtaining a starting model for the structure, and refining the model was presented. In addition, several areas in which neutron diffraction results have had a significant impact have been discussed. At the present time, data collection and analysis procedures at steady-state reactor sources are fairly routine and these facilities are being used by a growing number of chemical crystallographers. New pulsed spallation and steady-state neutron sources offer the potential of higher overall data rates and the use of smaller crystals approaching the size used for conventional x-ray studies.