On the application of Flory-Huggins and integral equation theories to asymmetric hard sphere mixtures

Flory-Huggins (FH) and integral equation theories (IETs) are used to descri be the equation of state and the relevant mixing properties of hard sphere binary mixtures in the limit of high size-asymmetry. The results are compar ed with those obtained from the heuristic equation of state of Mansoori (BM CSL) [J. Chem. Phys. 54, 1523 (1971)] and with the Flory-Huggins scheme of other authors. By choosing a physical recipe for the volume fractions of th e two species in the mixture FH theory is shown to be a good approximation to the entropy and the Gibbs free energy of mixing, which shows improvement at high size-asymmetry. In addition, the results of the IETs are found to be in overall quantitative agreement with BMCSL. The implications of our st udy concerning colloidal systems are discussed. (C) 1999 American Institute of Physics. [S0021-9606(99)50739-3].