An advanced dielectric continuum approach for treating solvation effects: Time correlation functions. I. Local treatment

A local continuum solvation theory, exactly treating electrostatic matching conditions on the boundary of a cavity occupied by a solute particle, is extended to cover time-dependent solvation phenomena. The corresponding integral equation is solved with a complex-valued frequency-dependent dielectric function «~v!, resulting in a complex-valued v-dependent reaction field. The inverse Fourier transform then produces the real-valued solvation energy, presented in the form of a time correlation function ~TCF!. We applied this technique to describe the solvation TCF for a benzophenone anion in Debye ~acetonitrile! and two-mode Debye ~dimethylformamide! solvents. For the Debye solvent the TCF is described by two exponential components, for the two-mode Debye solvent, by three. The overall dynamics in each case is longer than that given by the simple continuum model. We also consider a steady-state kinetic regime and the corresponding rate constant for adiabatic electron-transfer reactions. Here the boundary effect introduced within a frequency-dependent theory generates only a small effect in comparison with calculations made within the static continuum model. © 1998 American Institute of Physics. @S0021-9606~98!50403-5#