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M. Hilczer and M. Tachiya
[J. Mol. Liq.,Vol.64, pp.113-121, 1995]
The Molecular Dynamics method of computer simulation has been applied to evaluate the statistical distribution of the electrostatic potential difference eDeltaV between donor and acceptor sites immersed in acetonitrile solvent. By using this distribution the electron transfer rate constant for considered molecular systems has been calculated as a function of the free energy change of the reaction, DeltaG. This dependence has been compared with the corresponding result calculated on the basis of the dielectric continuum model (Fig. 1). It appears that a molecular model of solvent causes the shift of the inverted region for the charge separation reaction towards more negative values of DeltaG. Consequently, the inverted region starts in the range of DeltaG which is not accessible by experimental measurements. An estimation of the quantum correction to potential difference distribution has been also performed. The correction calculated using the time correlation function of fluctuations in eDeltaV is found negligible.
Fig. 1. Second-order diffusion-mediated rate constant ks of the charge separation in acetonitrile solution as a function of the free energy change DeltaG, calculated for the molecular model (full line) and for the continuum model of solvent (broken line).