Pair distribution functions (PDF, 3D-PDF and 3D-ΔPDF )

Abstract Following the success of the powder PDF method as a probe of local structure in all kinds of disordered materials the chapter describes the development of three dimensional single crystal PDF methods (3D-PDF and 3D-ΔPDF). The limitations of powder PDF that result from the powder induced orientational averaging are explored by comparing what the method can achieve compared to single crystal diffuse scattering analysis for a well known example. The 3D-ΔPDF method is demonstrated by a study of ionic correlations in sodium-intercalated V2O5. 3D-ΔPDF provides a significant advance in the study of diffuse scattering and disorder. One of the main reasons is that ΔPDF maps can be generated directly from the observed data and are generally much easier to interpret than the diffuse scattering itself.