The model consists of three-layer spheres, the inner one corresponding to the core of the particle with the surfactant adsorbed with hydrophobic and hydrophilic layers. The thickness and electronic densities of the surfactant layers have been fixed at 1.5 nm for the hydrophobic chains and 0.9 nm for the polar heads with corresponding electronic densities of 404 e/nm and 265 e/nm 3 respectively. The electronic density of the core has been set to 234 e/nm 3 in accordance with crystalline density. The fraction of particles corresponds to the proportion of particles necessary to fit the observed intensity with respect to the maximum concentration of particles possible if all the material is present in the form of particles.