COMPUTER-SIMULATION OF THE CHEMICAL-POTENTIALS OF BINARY HARD-SPHERE MIXTURES

An efficient, recently proposed, method for calculating the chemical p otentials of hard-sphere fluids up to very high densities by computer simulation is applied to the case of binary additive hard-sphere mixtu res. Mixtures are studied with diameter ratios 0.9, 0.6, and 0.3 at pa cking fractions up to eta = 0.49, for several mole fractions. This pap er is believed to give the first direct calculation of the chemical po tentials of such mixtures by computer simulation techniques. In additi on, pair distribution functions are simulated and compressibility fact ors calculated from the contact values of these. More particles are us ed than in earlier works and many more configurations generated. The r esults are used to test the BMCSL equation of state and systematic dev iations are found whose magnitudes increase in systems with large sphe re size ratios at small concentrations of the larger component. Two ad ditional routes are explored for calculating the chemical potentials. One is based on a new version of the Gibbs-Duhem equation that relates mole fraction derivatives of the chemical potentials at constant pack ing fraction. The other route utilizes only the contact values of the pair distribution functions. All three methods are in excellent mutual agreement.