Diffuse scattering and partial disorder in complex structures

Abstract

The study of single-crystal diffuse scattering (SCDS) goes back almost to the beginnings of X-ray crystallography. Because SCDS arises from two-body correlations, it contains information about local (short-range) ordering in the sample, information which is often crucial in the attempt to relate structure to function. This review discusses the state of the field, including detectors and data collection and the modelling of SCDS using Monte Carlo and ab initio techniques. High-quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing ever more detailed and quantitative analyses to be undertaken, and opening the way to approaches such as three-dimensional pair distribution function studies (3D-PDF) and automated refinement of a disorder model, powerful techniques that require large volumes of low-noise data.

Diffuse single-crystal scattering corrected for molecular form factor effects

“…Numerous different types of disorder exist; see Welberry & Weber (2015) for a recent review. Strictly speaking, any deviation from a perfect average crystal structure will cause diffuse scattering.…”

“…Many different approaches for the interpretation of diffuse scattering data exist (see Welberry & Weber, 2015). For most disordered structures solved so far a unique approach was taken and a specific model was developed.…”

Local disorder in Na0.5Bi0.5TiO3-piezoceramic determined by 3D electron diffuse scattering

“…Computer simulations of disordered structures can aid the interpretation of diffuse scattering data and both qualitative and quantitative models can be obtained in this way 56,57 . In the present work DISCUS 47,48 was used to develop a model for the local disorder in 85NBT-10BKT-5BT ternary ceramic that explains the observed superstructure reflections and diffuse scattering intensities.…”

Characterization of Pb-Free KNbO3- and (Na,Bi)TiO3-Based Piezoelectric Single-Crystals Using X-ray and Neutron Diffraction

“…Using tools of classical crystallography, the long-range atomic structure can be determined accurately by noting the position and the area of well-marked intense peaks in the diffraction pattern known as Bragg peaks. Instead, the correlated atomic disorder within nanoscale domains needs to be determined from the diffuse scattered intensities in between the Bragg peaks [49][50][51]. Diffraction experiments of high-quality single crystals enables measurement of such diffuse scattering signatures in reciprocal space in much more details than what can be achieved in polycrystalline powder samples.…”