Thermodynamic perturbation theory for multipolar and ionic liquids

We extend earlier work of ours on the use of Padé approximants in the theory of multipolar and ionic potentials. The new features are (i) extension of our work to mixed multipole terms and inclusion of polarizability, (ii) formulation and implementation of a systematic means of getting analytic approximations for all the two-body and three-body terms appearing in the theory, (iii) assessment of the ionic Padé results in the low-concentration region important in ionic-solution applications, (iv) use of the Padé in a mixed perturbation theory of improved accuracy in that low-concentration regime. The results of (iii) and (iv) are used to study the remarkable lowdensity charged-sphere critical point recently discovered by Stell, Wu, and Larsen.