The depletion potential in non-additive hard-sphere mixtures

We show that the density functional treatment (DFT) developed for additive hard-sphere mixtures can be employed directly to determine the depletion potential in mixtures where the diameters are non-additive. This enables us to calculate, within the same theoretical framework, depletion potentials for models which range from additive hard-spheres to the extreme non-additive Asakura-Oosawa model of colloid-ideal polymer mixtures. We find that for intermediate degrees of non-additivity the depletion potential between two big spheres, at a fixed density of small spheres, can be more attractive (as measured by the second virial coefficient B(2)) than in the Asakura-Oosawa limit.