Small-angle scattering data analysis in GSAS-II

The General Structure Analysis System II (GSAS‐II) now contains modules for the analysis of small‐angle X‐ray scattering data. This includes processing of two‐dimensional images to create corrected one‐dimensional patterns, analysis via maximum entropy or total nonnegative least‐squares methods of the size distribution, assuming polydispersity, in the dilute limit, and modeling of the one‐dimensional data with combinations of Guinier/Porod, Porod, both dilute and condensed populations of scattering objects, and Bragg scattering components; slit smearing corrections can be applied where needed. GSAS‐II can apply these modeling tools over a sequence of data collected while some experimental condition is varied. This sequential refinement result can then be subjected to a post refinement analysis to determine global parameters encompassing the entire experiment.