3D-ΔPDF Investigations of Structural Phase Transitions*

By exploiting a new generation of fast area detectors with wide dynamic range optimized for high-energy x-rays, it is possible to measure single crystal total scattering, S(Q), over large volumes of reciprocal space encompassing thousands of Brillouin zones in under 20 minutes. This allows detailed investigations of the temperature evolution of both weak Bragg peaks from modulations in the long-range crystal structure and diffuse scattering from short-range fluctuations in the atomic order. S(Q) can be transformed into real space to generate “difference” pair-distribution-functions (3D-ΔPDF), a powerful way of eliminating the average crystal structure to reveal subtle structural modifications and determine the correlation length of atomic fluctuations above and below T_c, all without detailed simulations.¹ I will show examples of 3D-ΔPDF applied to both long-range and frustrated short-range structural transitions in correlated electron systems and intercalation compounds.

1) Krogstad, M. J. et al. Reciprocal space imaging of ionic correlations in intercalation compounds. Nature Materials (2019). doi:10.1038/s41563-019-0500-7.