On the Concentration Fluctuations of a Binary Mixture of Hard Spheres
Abstract We have computed the concentration fluctuations, Scc(0), in a binary mixture of hard spheres on the basis of the Percus-Yevick compressibility (PYC), Percus-Yevick virial (PYV) and Mansoori- Carnahan-Starling (MCS) equations of state. We have also used the Flory-Huggins (FH) model for an athermal solution as a first approximation to the hard sphere description. At fluid packing fraction values, the PYC and MCS theories give similar Scc (0) results, whereas the differences between these and those derived from the PYV equation are more significant. The FH model appears to give rather bad results, which is consistent with the studies of other authors on the entropy of mixing of a binary mixture of hard spheres. The impossibility of a fluid-fluid phase transition in this kind of system is clearly shown by the behaviour of Scc (0) in any of the theories studied.