An analytic treatment of the first-order correction to the Poisson-Boltzmann interaction free energy in the case of counterion-only Coulomb fluid

The author has computed the first-order (correlation) correction to the Poisson-Boltzmann result for the interaction energy of two charged surfaces immersed into a counterion-only Coulomb fluid. The cases of small and large coupling were amenable to analytic treatment in the saddle-point approximation.