Structure/microstructure analysis of nanocrystalline materials

Odd profile shapes, deeply anisotropic line-profile broadening, unexpected features are sometimes observed in X-ray powder diffraction patterns. Even apparently well-behaving data lead sometimes to questionable refinement results (e.g. apparent polymorphism in transformations, unrealistic thermal parameters) in which materials' physics contrasts with the hypotheses on which the analysis method is based (e.g. 3D-periodic lattice). Complementary information is usually needed in those cases, together with new analysis tools able to cope with the real physical environment in which the problem is re-framed. A couple of such tools are the Whole Powder Pattern Method[1] that can provide microstructure information in simple cases, and the DIFFaX+[2] approach, able to deal with traditional, layered and modular structures showing a local or global reduction of the lattice symmetry due to the presence of defects. Basics and examples of both methods will be shown and commented. References 1. P. Scardi, M.Leoni Acta. Crystallogr. (2002), A58, 190. 2. M. Leoni, A. Gualtieri, N. Roveri J. Appl. Crystallogr. (2004), 37, 166.