Local strain, structured diffuse scattering and oxygen/fluorine ordering in transition metal oxyfluorides

Abstract

Conventional crystal structure refinements commonly report'randomanion site occupancies for the anion, or X, site positions of many metal oxyfluoride phases despite compelling evidence suggesting there must exist at least local O/F ordering. Diffraction evidence for such local ordering has been found to exist in a range of oxyfluorides in the form of structured diffuse scattering, typically a consequence of the correlated displacive relaxation of the cations induced by local O/F ordering.