Volume-explicit equation of state and phase behavior for mixtures of hard disks

In this study, a simple volume-explicit equation of state (EOS) for mixture s of hard disks is developed and tested using molecular dynamic simulation data for both additive and nonadditive hard disk mixtures over a wide range of size ratio, densities and compositions. The equation accurately represe nts the simulation data in most of the cases studied. The EOS is accurate f or all pressures or packing fractions in the case of additive and slightly nonadditive (nonadditivity parameter, Delta = + 0.05) mixtures (which is th e region of interest for real systems). For large nonadditivity, (Delta gre ater than or equal to + 0.2), the EOS is accurate only at low pressures/pac king fractions. The new equation also gives the exact second and third pres sure virial coefficients. The phase behavior of some nonadditive hard disks mixture is predicted using the developed equation. Symmetric phase boundar ies are obtained for equal size species and unequal size species result in asymmetric phase boundaries. The developed EOS can be used as the repulsive part in developing volume-explicit real fluid equations of state for molec ules on surfaces. (C) 2000 Elsevier Science B.V. All rights reserved.