hkl-based calculation of total scattering patterns from discrete and low-dimensional structure models using TOPAS.

If discrete or low-dimensional structure models are placed in large supercells in space group P1, the intrinsic periodicity of the Rietveld method is disrupted and their structural sites are scanned by millions of hkls. This allows a Rietveld-compatible calculation of diffuse scattering and small-angle scattering which is demonstrated here for a benzene molecule, a PbS quantum dot, a hydroxy-apatite nano-fibril and turbostratic carbon. Total scattering patterns are compared with the Debye scattering equation and accompanied by composite pair distribution function modelling using the same models.