  The mutual entropic depletion force felt by two solute "big" hard spheres
immersed in a binary mixture solvent of nonadditive "small" hard spheres is
calculated as a function of the surface-to-surface distance by means of
canonical Monte Carlo simulations and through a recently proposed
rational-function approximation [Phys. Rev. E \textbf{84}, 041201 (2011)]. Four
representative scenarios are investigated: symmetric solute particles and the
limit where one of the two solute spheres becomes a planar hard wall, in both
cases with symmetric and asymmetric solvents. In all cases, the influence on
the depletion force due to the nonadditivity in the solvent is determined in
the mixed state. Comparison between results from the theoretical approximation
and from the simulation shows a good agreement for surface-to-surface distances
greater than the smallest solvent diameter.
