Clays such as Montmorillonite present a unique challenge in unit cell and structure refinement due to their layered structures. The semi - crystalline nature of these materials, stemming from the disorder associated with the layered structures, gives rise to broadly asymmetric peak profiles that can be difficult to interpret.

Figure 1

Figure 1 shows a powder diffraction pattern collected on the Ultima IV multipurpose diffraction system for Montmorillonite clay together with a matching card of the phase from the ICDD database. Figure 2 shows the results of a Rietveld refinement of the material using a model obtained from the ICDD phases.

Figure 2