A MOLECULAR-DYNAMICS STUDY OF A 3 COMPONENT MIXTURE OF HARD-SPHERES WITH NEGATIVE NONADDITIVE INTERACTIONS

It is shown by molecular dynamics calculations that demixing occurs in a three component mixture of hard spheres with negative non-additive collision diameters (i.e. sigma12 < 1/2(sigma11 + sigma22)). The results of the molecular dynamics calculations are compared with theoretical predictions. Qualitative agreement for the phase behavior is found with the theory of regular mixtures and with one-fluid theories. The MIX1 perturbation theory, which gives the best prediction of the critical demixing densities in binary mixtures, fails to predict demixing in the three component mixture. For homogeneous states there is good quantitative agreement between compressibility factors obtained by molecular dynamics and the predictions of the Barker-Henderson 1-fluid theory.