Small Angle Scattering by Fractal Aggregates: A Numerical Investigation of the Crossover Between the Fractal Regime and the Porod Regime

摘要

Fractal aggregates are built on a computer using off-lattice cluster-clusteraggregation models. The aggregates are made of spherical particles of differentsizes distributed according to a Gaussian-like distribution characterised by amean $a_0$ and a standard deviation $\sigma$. The wave vector dependentscattered intensity $I(q)$ is computed in order to study the influence of theparticle polydispersity on the crossover between the fractal regime and thePorod regime. It is shown that, given $a_0$, the location $q_c$ of thecrossover decreases as $\sigma$ increases. The dependence of $q_c$ on $\sigma$can be understood from the evolution of the shape of the center-to-centerinterparticle-distance distribution function.