The X-ray atomic pair distribution function (PDF) is an X-ray scattering technique used to study the local structure of materials at the atomic scale. It involves collecting scattering data at very high angles using high-energy powder diffraction, which is then processed with a Fourier transform to produce the PDF data. This technique provides a quantitative histogram of inter-atomic distances, allowing for local structure refinement similar to how Bragg diffraction data is used for average structure refinement.
PDF is versatile and can be applied to solids, amorphous materials, and liquids. It is particularly useful for understanding the local structure of materials, which is often key to their properties. The technique has wide applications in fields such as battery and fuel cell materials, pharmaceuticals, and earth sciences.