For this work, the two relevant contributions are the solvent and cross terms, I vv (q) and I c (q), i.e. with g 0 w l wm = 1. The fundamental measurable quantity for these two terms, agnostic to the nature of the scatterer, is the structure factor S lm (q), which for uniform, isotropic systems comprised of particles of type m and l (with at least one type within the solvent) can be defined as :