A structural comparison of models of colloid-polymer mixtures

We study the structure of colloidal fluids with reference to colloid-polymer mixtures. We compare the one-component description of the Asakura-Oosawa (AO) idealization of colloid-polymer mixtures with the full two-component model. We also consider the Morse potential, a variable range interaction, for which the ground state clusters are known. Mapping the state points between these systems, we find that the pair structure of the full AO model is equally well described by the Morse potential and the one-component AO approach. We employ a recently developed method to identify in the bulk fluid the ground state clusters relevant to the Morse potential. Surprisingly, when we measure the cluster populations, we find that the Morse fluid is significantly closer the full AO fluid than the one-component AO description.