Applied Crystallography

Chemical Crystallography

Chemical crystallography is the application of diffraction techniques to the study of structural chemistry. A frequent purpose is the identification of natural products, or of the products of synthetic chemistry experiments; however, detailed molecular geometry, intermolecular interactions and absolute configuration can also be studied. Structures can be studied as a function of temperature, pressure or the application of electromagnetic radiation, or magnetic or electric fields: such studies comprise only a small minority of the total. While the majority of structure analyses are routine, the need to determine structures from increasingly difficult samples continually presents new challenges: limited crystal quality can appear as weak diffraction, disordered atoms, twinning or large regions of diffuse solvent. Some of these difficulties can be at least partially overcome by employing more powerful radiation sources. Because the extent of diffraction depends on the number of electrons an atom has, identifying the positions of hydrogen atoms using X-ray diffraction can be problematic, as can distinguishing atoms with similar atomic numbers.