X-ray diffraction by crystalline materials

Abstract

Diffraction ofX-rays by crystals offers the unique possibility to determine at atomic resolution the three-dimensional structure of solids. This opportunity is exploited by solid state chemists or by mineralogists to study the structure of crystals, by chemists to determine the structure of molecules and by molecular biologists to investigate structure and properties of living organisms molecules, like proteins, nucleic acids etc. In this chapter, after a brief introduction on crystals and crystal symmetries, the general principles of diffraction are introduced, then the reader is made familiar with the mathematical formalism of scattering and diffraction. The physical principles of diffraction by crystals are then introduced, and finally the phase problem in crystallography is presented and the main methods to solve it are shortly outlined. Few notes on the refinement process and on powder diffraction are also reported.