59th Annual Report on Research 2014

Electron transfer process in ionic fluid is studied under linear response approximation with a molecule Debye-HŸckel theory. The reorganization energy which serves as a crucial parameter in Marcus' theory, could be derived from the free energy profile for reactant or product. As a consequence of linear response, the free energy profile is a quadratic function of a reaction coordinate such as the vertical energy gap. Furthermore, it is noted that the fluctuation and mean value of the vertical energy gap are related to each other by the fluctuation-dissipation relation, and hence both of them could be used to evaluate the reorganization energy. Our molecule Debye-HŸckel theory could be used to calculate the mean value of the vertical energy gap, from which the reorganization energy is calculated.

Out theory is applied to electron transfer process in homogenous ionic fluid and in an electric cell, where the reorganization energy from molecule dynamics simulations could be well reproduced by our theory prediction, which demonstrates the accuracy of our theory.

Here are the papers published from the support of this grant:

T. Xiao and X. Song, A molecular Debye-Huckel approach to the reorganization energy of electron transfer reactions in an electric cell, J. Chem. Phys., 141,134104(2014).

T. Xiao and X. Song, Reorganization energy of electron transfer processes in ionic fluids:a molecular Debye-Huckel approach , J. Chem. Phys., 138,114105 (2013).

We are also in the process of extending the molecular Debye-HŸckel theory to time dependent processes. In particular we are using the generalized collective mode (GCM) method to construct frequency and wavenumber dependent dielectric function that satisfies the dispersion relation from molecular dynamics simulation of the neat ionic fluid (NaCl melt in our case). Using this dielectric function we can study solvation dynamics in ionic fluids and spectral density of electron transfer reactions in ionic fluids of any coupling strength, thus extending the molecular Debye- HŸckel theory to dynamical processes in ionic fluids. A manuscript is in the preparation based upon this work.