A new analytical equation of state for additive hard sphere fluid mixtures

A study has been made of the relation between the equation of state of addi tive binary hard sphere fluid mixtures and the equation of state of a pure hard sphere fluid for the same packing fraction. An analysis of the existin g simulation data for a wide variety of compositions of the mixture and dia meter ratios up to 1/0.2 makes it possible to conclude that the ratio of th e excess compressibility factor of the mixture to that of the pure fluid is , to a very good approximation, a linear function of the packing fraction. This suggests the possibility of deriving the equation of state of the mixt ure from that of the pure fluid by using the second and third virial coeffi cients of the mixture, which are known analytically, to reproduce the linea r relation mentioned above. When a suitable equation of state is chosen for the pure fluid, the results from the equation of state of the mixture thus obtained are in excellent agreement with simulation data. The predictions for the fourth and fifth virial coefficients also are very accurate compare d with known numerical data.