Total scattering - that is an absolutely normalised powder diffraction pattern including the diffuse scattering component - may be used to extract the average crystal structure (via Rietveld refinement) and local atom pair correlations (via a sine Fourier transform of the data).  Atomistic models that are derived from this local and average information may be used to aid the understanding of crystal structures and this approach is especially helpful if the structures are complicated by a degree of local disorder. 

I will illustrate how total scattering data may be collected, analysed and modelled using a number of examples and highlighting the additional insight made possible from this analysis over and above an interpretation based on the average structure alone.  In this talk there will also be examples from our recent work, which uses RMCProfile modelling [1], including a structural explanation of pressure-induced amorphisation and negative thermal expansion in ZrW₂O₈ [2-4] and how weak argentophilic interactions govern the colossal (positive and negative) thermal expansion in Ag₃[Co(CN)₆] [5].

[1] M G Tucker, D A Keen, M T Dove, A L Goodwin and Q Hui J. Phys.: Condensed Matter 19 335218 (2007)
[2] D A Keen, A L Goodwin, M G Tucker, M T Dove, J S O Evans, W A Crichton and M Brunelli, Phys. Rev. Lett. 98 225501 (2007)
[3] M G Tucker, A L Goodwin, M T Dove, D A Keen, S A Wells and J S O Evans, Phys. Rev. Lett. 95 255501 (2005)
[4] M G Tucker, D A Keen, J S O Evans and M T Dove, J. Phys.: Condensed Matter 19 335215 (2007)
[5] A L Goodwin, M Calleja, M J Conterio, M T Dove, J S O Evans, D A Keen, L Peters and M G Tucker, Science 319 794-797 (2008)

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