Rooks, J.Gilbert, P. H.Porcar, L.Liu, Y.Butler, P.2023-08-032023-08-032023-06Rooks, Jack, Peter H. Gilbert, Lionel Porcar, Yun Liu, and Paul Butler. “Anisotropy Factors in Small-Angle Scattering for Dilute Rigid-Rod Suspensions.” Journal of Applied Crystallography 56, no. 3 (June 2023): 683–96. https://doi.org/10.1107/S1600576723002182.1600-5767https://udspace.udel.edu/handle/19716/33052This article was originally published in Journal of Applied Crystallography. The version of record is available at: https://doi.org/10.1107/S1600576723002182Alignment of anisotropic particles along specific orientations influences the mechanical and rheological properties of a material. Small-angle scattering techniques are widely used to probe this alignment through analysis of anisotropic two-dimensional scattering intensity patterns. The anisotropy factor is the simplest and most common quantitative parameter for describing scattering anisotropy, especially in systems containing rod-like particles, and there are several methods for calculating this factor. However, there has been no systematic study comparing these methods while also evaluating the limitations imposed by non-idealities from instrumentation or polydisperse morphology. Three of the most common methods for calculating an anisotropy factor are examined here and their effectiveness for describing the orientation of a theoretical cylinder is evaluated. It is found that the maximum theoretical value of 1 for the anisotropy factor is only accessible at certain values of scattering vector q. The analysis details recommendations for q-range selection and data binning, as these influence the calculations. The theoretical results are supported by experimental small-angle neutron scattering data for a wormlike micelle solution undergoing shear, where different calculation methods yield distinct quantifications of anisotropy.en-USsmall-angle neutron scatteringanisotropy factorsalignmentwormlike micellesanisotropysmall-angle scatteringArticle