In the formalism given in Figure , there is thus a combinatoric entropy of binding for both polymers, with respect to the polymer-ion and polymer-polymer binding sites on both chains, on the first two terms. The subsequent two terms account for the change in translational entropy upon undergoing a 'binding' event, and finally the last two terms account for the free energies of binding that result from the local correlations. As a reminder, these terms are in addition to both the mixing entropy and RPA terms that were also included in the Qin-Larson formalism, 100 but can be formed from the standard ring diagrams that emerge from the first-and second-order products of f -bonds. Thus, these 'ion binding' terms are an additional contribution to coacervate models, beyond the mixing entropy and RPA free energy contributions.