On the use of multiple interpolation series in scaled particle theory: improved predictions and limitations

We propose further modifications to recent formulations of the scaled particle theory (SPT) of hard particle fluids. In any formulation of SPT, a number of conditions are applied to the central function G. As the exact form of G is unknown, a form must be assumed. Representing G with more than one series has recently been shown (Siderius and Corti, J. Chem. Phys. 127, 144502, 2007) to lead to improved planar surface tension predictions with little change in the already accurate pressure, excess chemical potential and fluid structure predictions. Another condition on G that includes the curvature of the radial distribution at contact was not, however, invoked in this previous work. We incorporate here this additional condition into the multiple series approach, resulting in further improvements to the SPT predictions. We also consider a number of permutations of the multiple interpolation series to explore the limitations of this approach and again find that increasing the number of series will not by itself lead to better predictions of the properties of the hard sphere fluid.