Discreteness-of-solvent effects in Marcus equations in the mean spherical approximation

In the Marcus theory of electron transfer the outer sphere contribution to the free energy of activation G sub os is usually computed from Born continuum dielectric formula. The Mean Spherical Approximation gives systematic corrections to this quantity, which for a solvent of hard dipolar spheres can be explicitly calculated. The contributions are of two kinds: The polarization of the solvent by the charges, and the electrostriction effects, which usually are small. The effects of ion association are included using recent results for sticky potential models. These corrections also can be incorporated into the dynamical theories of solvation effects.