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 binar y nonadditive hard sphere mixtures having equal collision diameters (d (11)=d(22)=d) between like species, but having an unequal collision di ameter (d(12)) between unlike species. For this purpose, we have gener ated 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 t o test the van der Waals one-fluid model of mixtures and the modified Martynov and Sarkisov integral equation [Mol. Phys. 59, 275 (1986)]. S hort-range structures at high density reveal a broad peak in heterocoo rdinated packing and a minimum in homocoordination as d(12) is reduced below d. The present analysis also strongly indicates, in agreement w ith available data, a fluid-fluid phase change at high density when d( 12)>d.