Total Scattering: Pair-Distribution Function Analysis of Amorphous or Partially Crystalline Materials
Conventional X-ray diffraction experiments cannot provide detailed structural information about amorphous or partially crystalline disordered compounds. For amorphous or nanocrystalline samples, total scattering experiments can be used which take into account not only Bragg reflections but also diffuse scattering components. Pair distribution function curves (PDF) are obtained from the Fourier transformation of scattering data. These curves describe the distribution of interatomic distances between pairs of atoms and thus the local structure.
An example of the potential of PDF analyses are investigations on the formation of PtNi nano-alloys in porous graphitic hollow spheres, a material that has also been tested as electrode material in fuel cells. From temperature dependent PDF measurements, order and disorder phenomena of the alloy could be identified and correlated with heating and cooling rates. Another example are in situ PDF investigations on the crystallization of metal oxides, which can be used as photocatalysts. Both the formation of structural formation blocks from molecular precursors in highly diluted solutions and the temperature-dependent crystallization and phase transformation can be observed using in situ PDF analyses.
Ş. Ortatatlı, Ş., Knossalla, J., Schüth, F., Weidenthaler, C. “Monitoring the formation of PtNi nanoalloys supported on hollow graphitic spheres using in situ pair distribution function analysis”, Phys. Chem. Chem. Phys., 2018, doi: 10.1039/c7cp07840d.