SMALL-ANGLE SCATTERING FROM PARTICLES HAVING AN IRREGULAR INNER STRUCTURE

A model is presented for the scattering pattern of a dilute dispersion of particles having an irregular inner structure, made of two phases randomly distributed. For isotropic particles in a dispersant medium, the correlation function of the inner structure has, in the limit of s mall distances, the same exponential form as that for a two-phase syst em, provided that the characteristic length scale of the inner structu re is small compared to the particle dimension. The scattering pattern of spherical particles is presented in a form suitable for analysis u sing the contrast-variation method. The cross-term, related to the ori entation average of the scattering amplitude, is absent for a random i nner structure. The heterogeneous part of the scattering curve is the same as for a randomly distributed two-phase structure. The sphere met hod is used to simulate the scattering behaviour of particles having a n irregular inner structure and to demonstrate the validity of the pro posed model.