A computer program for structural refinement from thin film XRD patterns

The number of people involved in structural refinements from XRPD (X-ray Powder Diffraction) is growing continuously, beyond the specific field of crystallography. Increasingly more interest comes from other disciplines like materials science. In this type of applicative research, it frequently occurs that the materials under study are not powders, nor may be reduced to powders, but are polycrystalline bulk materials or thin films. In the latter case, when the thickness of the layers is comparable with the penetration depth of the radiation in the material, or when the distribution of the phases is not random, the specific nature of the studied sample must be considered. The Rietveld method, and other Whole Powder Pattem Fitting (WPPF) techniques may still be of great interest, provided that a suitable model for the layer structure is introduced in the conventional procedures adopted for XRPD studies. In the present work we discuss one such application, that led to the development of Xmas, a new software tool for an easy modelling (and simulation) of XRD data from multilayer materials. The computer codes may also be used for powder and polycrystalline bulk samples, therefore the proposed programs may be considered as powerful tools for an easy access to structural refinement and WPPF techniques for a non-expert public.