Coherence of the mosaic blocks in X-ray diffractography

Abstract

It is shown that the coherence properties of mosaic blocks can be studied both qualitatively and quantitatively. The idea behind the calculation is as follows: the mosaic blocks are considered to be a secondary source of X-rays and their coherence properties are then investigated by the usual methods used in the theory of coherence properties of light. The considerations given in this paper allow a more detailed examination as to the complexity of the origin of the diffraction by real crystals and also theoretically give reasons for the hitherto intuitively presented assumptions that mosaic blocks or powder crystal particles are mutually incoherent. From these calculations it also follows that the coherence of mosaic blocks depends not only on the crystallographic point of view, but also on the coherence properties of the X-rays.