Realistic, quantitative descriptions of electron-transfer reactions: diabatic free-energy surfaces from first-principles molecular dynamics

摘要

A general approach to calculate the diabatic surfaces for electron-transferreactions is presented, based on first-principles molecular dynamics of theactive centers and their surrounding medium. The excitation energycorresponding to the transfer of an electron at any given ionic configuration(the Marcus energy gap) is accurately assessed within ground-statedensity-functional theory via a novel penalty functional foroxidation-reduction reactions that appropriately acts on the electronic degreesof freedom alone. The self-interaction error intrinsic to commonexchange-correlation functionals is also corrected by the same penaltyfunctional. The diabatic free-energy surfaces are then constructed fromumbrella sampling on large ensembles of configurations. As a paradigmatic casestudy, the self-exchange reaction between ferrous and ferric ions in water isstudied in detail.