General theory of the effect of granularity in powder X-ray diffraction

The effect of granularity in powder X-ray diffraction is reviewed, and the shortcomings of previously developed models in explaining this effect are described. A new physical model encompassing all aspects of this phenomenon is proposed. Mathematical formulae based on the model are derived, and their limit cases are discussed. Values of the theoretical intensities from the model are compared with results from a specially designed experiment.