Single Crystal Diffuse X-ray Scattering Using Continuous Rotation*

Single crystal diffuse scattering provides a measure of the 3D pair distribution function and is thus useful for investigating short-range order in materials. Using very bright synchrotron x-ray sources and fast area detectors, large volumes of reciprocal space can be mapped quickly with a dynamic range large enough to measure both Bragg peaks and the much weaker diffuse scattering. With the appropriate tools for processing and analyzing large data sets (10 to 30GB), this technique can be used to track changes in the defect structures of a material as a function of different parameters, providing a sensitive and efficient method for investigating phenomena associated with disorder. We have been developing methods of measuring diffuse scattering using continuous sample rotations (shutterless mode) at the Advanced Photon Source, and will show data from several systems, including iron pnictides, for a range of temperatures and doping levels.