The conventional scaled particle theory (SPT) [1] combines geometric information on the structural response of hard sphere particles due to the insertion of a cavity with statistical mechanical formalism, to predict the thermodynamics of hard particle systems. In addition to the hard sphere fluid, SPT has been successfully applied to other systems [2-6], including fluid mixtures and crystals. We propose a generalization of scaled particle theory that allows the calculation of the hard sphere pair correlation function g(r) by considering the insertion of two equal-sized spherical exclusion regions or cavities into a fluid of hard spheres separated by a distance r. We compare the prediction of the hard sphere fluid pair correlation function and pressure from the extended SPT with theoretical and computational results from the literature. We also discuss results for the surface tension and virial coefficients obtained through an iterative density expansion procedure as well as the application of the extended SPT to the study of solvation phenomena.

[1] H. Reiss, H. L. Frisch, and J. L. Lebowitz, J. Chem. Phys. 31, 369 (1959).

[2] J.L. Lebowitz, E. Helfand, and E. Praestgaard, J. Chem. Phys. 43, 774 (1965).

[3] A.B. Ritchie, J. Chem. Phys. 46, 618 (1967).

[4] R.M. Gibbons, Mol. Phys. 17, 81 (1969).

[5] F.H. Stillinger, J. Solution Chem. 2, 141 (1973).

[6] M.A. Cotter and F.H. Stillinger, J. Chem. Phys. 57, 3356 (1972).