The RED extinction model. III. The case of pure primary extinction

Abstract

Bragg diffraction in nearly perfect crystals is treated within the framework of the random elastic deformation (RED) model. Similar to the previous applications it is again assumed that each individual reflection event takes place within an elastically deformed domain and hence may be described by either an exact or a quasiclassical solution to the Takagi–Taupin equations. But because of the high degree of perfection and/or small thickness of the crystal the interaction is confined to one single domain so that the total reflected intensity is obtained just by summing up the contributions from the whole ensemble of domains characterized by different values of the deformation gradient and thickness. The present approach profoundly differs from Kato's statistical dynamical theory which starts with the averaging procedure within the Takagi–Taupin equations before solving them.