Solvent free energies for electron transfer at a solution/metal interface. Effect of ion charge and external electric field

Solvent free energies for electron transfer reactions at the water/Pt interface are calculated using molecular dynamics umbrella sampling for different ion charges and external electric fields. In all cases, the free energy curves as a function of solvent coordinate are in reasonable agreement with the linear response approximation, with the largest deviations observed for an electron transfer involving a neutral atom. Although the metal surface in the model Hamiltonian discussed here has only a minor effect on the shape of the free energy curves, it does introduce significant correlations between inner- and outer-solvent shell fluctuations as the charge on the ion is decreased.