Dynamical neutron diffraction on perfect crystals

The theory of phenomena occurring in the interaction of a thermal-neutron beam with a regular periodic set of nuclei, which represents a perfect crystal, and the results of relevant experimental investigations of such phenomena are described. The development of studies in these realms has led to the emergence of new fields of investigations in neutron optics, such as neutron interferometry and neutron topography. Neutron crystal spectrometers that possess a high angular and a high energy resolution and which serve for studying small-angle and diffuse scattering have been created. The possibilities for developing new theoretical descriptions of dynamical neutron diffraction and for performing new experiments with neutron beams are discussed.