Small-angle scattering from collections of interacting hard ellipsoids of revolution studied by Monte Carlo simulations and other methods of statistical thermodynamics

Computer simulations using Monte Carlo methods are used to investigate the effects of interparticle correlations on small-angle X-ray and neutron scat tering from moderate or highly concentrated systems of ellipsoids of revolu tion. Both oblate and prolate ellipsoids, of varying eccentricities and con centrations, are considered. The advantage with Monte Carlo simulation is t hat completely general models, both regarding particle shapes and interacti on potentials, can be considered. Equations are also given that relate the nonideal part of the chemical potential, beta mu(ni), with the scattering a t zero angle, I(0), and the compressibility factor, z. The quantity beta mu (ni) can be obtained during the Monte Carlo simulations by using Widom's te st-particle method. For spherical particles, the simulations are compared w ith approximation formulas based on the Percus-Yevick equation. A method is also suggested for the calculation of both beta mu(ni) and z from experime ntal values of I(0) recorded as a function of concentration.