AN ANALYTIC EQUATION OF STATE AND STRUCTURAL-PROPERTIES OF NONADDITIVE HARD-SPHERE MIXTURES

We present a new analytic fluid-phase equation of state (EOS) of binary nonadditive hard sphere mixtures having equal collision diameters (d(11)=d(22)=d) between like species, but having an unequal collision diameter (d(12)) between unlike species. For this purpose, we have generated EOS data by Monte Carlo simulations over a wide range of density, composition, and d(12) The analytic EOS produces reliable results for d(12)greater than or equal to d and d(12)<d. These results are used to test the van der Waals one-fluid model of mixtures and the modified Martynov and Sarkisov integral equation [Mol. Phys. 59, 275 (1986)]. Short-range structures at high density reveal a broad peak in heterocoordinated packing and a minimum in homocoordination as d(12) is reduced below d. The present analysis also strongly indicates, in agreement with available data, a fluid-fluid phase change at high density when d(12)>d.