Powder diffraction by layered minerals containing different layers and/or stacking defects. Comparison between Markovian and non-Markovian models

The models used up to now for the calculation of powder patterns of layer minerals containing defects have adopted a Markovian hypothesis for the law of defect occurrence. One consequence of this hypothesis is that in a powder obeying this law the particles differ in their contents (chemical composition and/or abundance of stacking defects). Another model can be considered in which the particles have identical contents of each type of layers or stacking defects. This is denoted here by the `identical contents crystal model' (ICC model). In this article are described: (i) the calculation of diffracted intensities for the ICC model and its comparison with that of the Markovian one, and (ii) the application of this calculation to a two-component mixed-layer system. It is shown which kind of modification of intensities or peak positions occur with the ICC model for thin crystals.