Nanostructured and Faulted Materials: is the Conventional Powder Pattern Obsolete?

When dealing with nanocrystalline materials, the PDF and the Debye approaches are usually considered as the only alternatives to the traditional Rietveld refinement. The comparison, however, is not fair; the Rietveld method, based on a 3D periodic lattice, cannot (easily) deal with diffuse scattering features or with non-crystallographic systems and does usually not consider microstructure in a physically meaningful way. However, by employing the Whole Powder Pattern Modeling (WPPM) algorithm [1], including the idea proposed in [2] to handle stacking defects, it can be shown that a wide set of diffuse features can be suitably considered also in a reciprocal space approach [3]. The information that can be obtained from a conventional powder pattern e.g. on the shape, size distribution and defects, can, in some cases, go beyond the limits of the proposed alternative approaches that might require longer or more complex experiments or data processing.