Thermodynamic properties of a polyelectrolyte solution containing a mixture of counterions of the same charge

Electrostatic internal and free energies are calculated for the cell model of a polyelectrolyte solution having two kinds of counterions of the same charge but different size. The calculation is based on the solution of the Poisson–Boltzmann equation obtained previously. The electrostatic contributions to the internal and free energies are presented as functions of valences, radii, and mole fractions of counterions, and their application to interpretation of experimental results is discussed.