The Darwin-Prins rocking curve for distorted crystals

Rocking curves (RC) of Darwin-Prins type of distorted crystals have been systematically studied with respect to various parameters which characterize the crystal and its deformation. The basic formula is given in an earlier paper [Kato (1990). Acta Cryst. A46, 672-681]. Through numerical analysis, characteristic features of RCs were deduced. In order to understand them, a simplified theory was developed based on a WKB approximation. Most of the features, in particular the oscillatory behaviour of RCs, could be interpreted by the geometrical configuration of the entrance surface and the bending C band, which was defined as a region where the local wave number is practically pure imaginary. The concept of the C band is analogous to the forbidden energy band of electrons popular in solid-state physics.