Investigating pair distribution function use in analysis of nanocrystalline hy­droxy­apatite and carbonate-substituted hy­droxy­apatite

Hy­droxy­apatite (HA) is a com­plex material, which is often nanocrystalline when found within a biological setting. This work has directly com­pared the structural characteristics derived from data collected using a conventional laboratory-based X-ray diffractometer with those collected from a dedicated pair distribution function (PDF) beamline at Diamond Light Source. In particular, the application of PDF analysis methods to carbonated HA is evaluated. 20 synthetic samples were measured using both X-ray diffraction (XRD) and PDFs. Both Rietveld refinement (of laboratory XRD data) and real-space refinement (of PDF data) were used to analyse all samples. The results of Rietveld and real-space refinements were com­pared to evaluate their application to crystalline and nanocrystalline hy­droxy­apatite. Significant relationships were observed between real-space refinement parameters and increasing carbonate substitution. Understanding the local order of synthetic hy­droxy­apatite can benefit several fields, including both biomedical and clinical settings.