Publisher Summary X-ray diffraction plays an important role in studies of the atomic structure of materials. The technique requires a beam of X-rays which scatter from a sample. The wave nature of the X-rays means that the scattering from different parts of the sample interferes and as the wavelength of X-rays is comparable to the atomic spacing of solids, the observed scattering is sensitive to the arrangement of the atoms. When the sample is a crystal, the scattering is found to occur at particular angles. This is a result of the interference among waves scattering from the periodic crystal structure. The angle through which the waves are scattered is the Bragg angle. The interference occursamong waves scattering from different planes of atoms that are perpendicular to the scattering vector. The scattering of X-rays is normally interpreted in the kinematical theory. In kinematical theory, the scattering is assumed weak. It is only necessary to take account of the scattering of the incident primary waves and the scattering of the diffracted waves by the crystal can be ignored. When the crystal is highly perfect, the kinematical theory is inadequate. Dynamical theory addresses the limitations of kinematical theory by including the interaction of both the incident and the diffracted waves with the crystal.