title: Effect of solvent polarization on the reorganization energy of electron transfer from molecular dynamics simulations.
abstract: The solvent contribution lambda(s) to the reorganization energy of electron transfer can be estimated from averages of the potential energy gaps between neutral-pair and ion-pair states over an ensemble of structures generated from molecular dynamics simulations. Invoking a Marcus-type two-sphere model for charge separation and recombination in an aqueous environment, we explored the effect of a polarizable force field and noted a strong reduction of lambda(s) (by approximately 45%) compared to the corresponding value obtained with a standard nonpolarizable force field. Both types of force fields yield lambda(s) values that in agreement with the Marcus theory, vary strictly linearly with the inverse of the donor-acceptor distance; the corresponding slopes translate into appropriate effective optical dielectric constants, epsilon(infinity) approximately 1.0+/-0.2 for a nonpolarizable and epsilon(infinity) approximately 1.7+/-0.4 for a polarizable force field. The reduction in the solvent reorganization energy due to a polarizable force field translates into a scaling factor that is essentially independent of the donor-acceptor distance. The corresponding effective optical dielectric constant, epsilon(infinity) approximately 1.80, is in excellent agreement with experiment for water.
authors.affiliation: Department Chemie, Theoretische Chemie, Technische Universität München, 85748 Garching, Germany.
authors.forename: Egor
authors.initials: E
authors.lastname: Vladimirov
authors.forename: Anela
authors.initials: A
authors.lastname: Ivanova
authors.forename: Notker
authors.initials: N
authors.lastname: Rösch