SCATTERING FUNCTIONS FOR MULTICOMPONENT MIXTURES OF CHARGED HARD-SPHERES, INCLUDING THE POLYDISPERSE LIMIT - ANALYTIC EXPRESSIONS IN THE MEAN SPHERICAL APPROXIMATION

We present a closed analytical formula for the scattering intensity fr om charged hard sphere fluids with any arbitrary number of components. Our result is an extension to ionic systems of Vrij's analogous expre ssion for uncharged hard sphere mixtures. Use is made of Baxter's fact or correlation functions within the mean spherical approximation (MSA) . The polydisperse case of an infinite number of species with a contin uous distribution of hard sphere diameters and charges is also conside red. As an important by-product of our investigation, we present some properties of a particular kind of matrices (sum of the identity matri x with a dyadic matrix) appearing in the solution of the MSA integral equations for both uncharged and charged hard sphere mixtures. This an alysis provides a general framework to deal with a wide class of MSA s olutions having dyadic structure and allows an easy extension of our f ormula for the scattering intensity to different potential models. Fin ally, the relevance of our results for the interpretation of small ang le neutron scattering experimental data is briefly discussed. (C) 1997 American Institute of Physics. [S0021-9606(97)52147-7].