Simulations of adiabatic bond-breaking electron transfer reactions on metal electrodes

Adiabatic electron transfer at metal electrodes accompanied by bond breaking is studied by molecular dynamic simulations in a two-dimensional model potential. In the simulations the redox system is coupled to a thermal bath that ensures proper statistical mechanics and provides the energy fluctuations required for the system to cross the activation barrier. The rate constants and transmission factors obtained from the simulations are analysed for various system parameters such as the applied overpotential and the strength of the interaction between the reactants and the electrode. A dependency of the rate constant on the friction parameter is also tested considering both isotropy and anisotropy effects. The Kramers turnover region is found in both cases, but the rate constant is much lower than predicted by the Kramers theory. In all simulations a strong saddle-point avoidance was observed. (C) 2002 Published by Elsevier Science B.V.