Quantum Simulation of Heterogeneous Electron Transfer Free Energies at the Water-Metal Interface
Technical rept. May 1993-May 1994
PENNSYLVANIA UNIV PHILADELPHIA DEPT OFCHEMISTRY
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The free energy for electron transfer is studied for the Fe2 Fe3 charge transfer system at the water-Pt111 interface. Classical adiabatic free energy curves are calculated along with an adiabatic curve based on the Anderson-Newns Hamiltonian. Reactive flux calculations are then performed on this curve to determine the effect of recrossings on the classical rate constant. These effects are not found to be large Kappa approx. 0.6 The solvent model is then extended to a quantum mechanical path integral version and quantum adiabatic free energy curves are calculated. The resulting quantum effects are found to be quite significant, illustrating that the same electrode overpotential does not necessarily result from the same free energy curves for the classical and quantum mechanical solvent models. These results suggest that classical models for water may not be adequate, or at least need to be modified, for accurate simulations of heterogeneous electron transfer.
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