MOLECULAR-DYNAMICS AND MEAN SPHERICAL APPROXIMATION RESULTS FOR SYMMETRICAL NONADDITIVE HARD-CORE YUKAWA MIXTURES

The thermodynamic properties of some symmetric hard core Yukawa mixtur es with positively and negatively nonadditive diameters are studied by molecular dynamics (MD) simulation, and the results compared with the predictions of the mean spherical approximation (MSA). MSA results fo r the compressibility factors are obtained by taking as reference the semiempirical equation of state proposed by Gazzillo and Pastore for s ymmetric nonadditive hard sphere fluids. Our calculations show that th e ''exact'' computer simulation data are, in general, closely approxim ated by the MSA energy route to the thermodynamic properties. For the largest positive nonadditivity considered in this paper, some discrepa ncies appear between the compressibility factors obtained by MD and th e MSA, but it is shown that the origin of the discrepancies lies in th e hard core part of the compressibility factor rather than in the MSA theory of liquids.