Density Functional Theory of Interactions Between Charged Macroions in Solution

ABSTRACTWe apply density functional theory to the screened interactions between macroions in solution. The approach incorporates the strong correlations between screening ions at high densities, and reduces to the Poisson-Boltzmann equations at low densities. Local density functional theory results for the interactions between parallel planes are within ˜ 1% of Monte Carlo (MC) and inhomogeneous hypernetted chain (IHNC) values when the plane separation L ≥ 50Å. Non-local effects are important for divalent ions at small separations and high surface charge densities. A simple weighted density approximation qualitatively reproduces MC and IHNC results in this regime, and provides a simple explanation for the onset of attractive interactions between like-charged plates.