A critical examination of the decoupling approximation for small-angle scattering from hard ellipsoids of revolution

The decoupling approximation, proposed by Kotlarchyk & Chen [J. Chem. Phys. (1983), 79, 2461–2469], is a first-order correction to the experimentally determined apparent structure factor that is necessary because of concentration effects in polydisperse and/or nonspherical systems. While the approximation is considered accurate for spheres with low polydispersity (<10%), the corresponding limitations for nonspherical particles are unknown. The validity of this approximation is studied for monodisperse dispersions of hard ellipsoids of revolution with aspect ratios ranging from 0.333 to 3 and a guide for its accuracy is provided.