Pair distribution function analysis

Pair distribution function (PDF) analysis enables researchers to gather previously unobtainable information about the organization of atoms in poorly crystalline materials. A diffractogram contains more information than just the Bragg peaks. Structural information about nanomaterials is present as broad, not-well defined features. Pair distribution function (PDF) analysis is an analytical technique that uses this information to reveal the nanostructure of materials. Usually nanomaterials have a certain degree of disorder; they can be nanocrystalline, liquid or amorphous.

The method

The pair distribution function describes the probability of finding two atoms separated by a certain distance in the material under investigation. The PDF method extracts structure-related information from powder diffraction data. Since the technique takes both Bragg and diffuse scattering into account, it provides information not only about the long-range (> 10 nm) atomic ordering, but also about the short-range ordering in materials.

The applications

PDF analysis is applied on all kinds of amorphous and nanocrystalline materials, such as silicon carbide, titanium dioxide and vitreous silica. The analysis requires short X-ray wavelengths to obtain useful resolution and, until now, has relied on the high quality X-ray beams from synchrotron sources.

Optimizing experiment time

Despite the advantages that measurements at synchrotron beam lines offer, in practice it can be difficult and time-consuming to get access to the required facilities. In order to make the best of the limited experiment time available, it is highly desirable to perform selective measurements on candidate samples in the research laboratory ahead of time.

Our solution

Total scattering experiments for PDF analysis can be performed in-house on the Empyrean system, equipped with an X-ray tube with silver anode for hard radiation experiments. Results obtained with this system allow for comparison with synchrotron data. The setup offers the ideal preparation and screening tool for synchrotron beam time. Thanks to the PreFIX concept for mounting of optical modules and sample stages the system is fully compatible with all other configurations.