Ab Initio Free Energy Surfaces for Coupled Ion-Electron Transfer
Abstract
The Marcus theory of electron transfer assumes that diabatic energy gaps are sampled from a single ensemble. This assumption can break down in spatially anisotropic environments, such as Faradaic reactions at electrochemical interfaces, where distinct solvent ensembles arise along a collective variable describing the anisotropy. Treating this collective variable as an additional reaction coordinate linearly independent from the Marcus reaction coordinate, we develop a formalism that enables calculation of the resulting Coupled Ion-Electron Transfer (CIET) free-energy surface directly from constrained ab initio trajectories. Applied to CO2 redox on a gold electrode, this method reveals strong coupling to the anisotropy, predicting significantly different activation barriers compared to either coordinate alone.
Keywords
Cite
@article{arxiv.2510.19106,
title = {Ab Initio Free Energy Surfaces for Coupled Ion-Electron Transfer},
author = {Ethan Abraham and Martin Z. Bazant and Troy Van Voorhis},
journal= {arXiv preprint arXiv:2510.19106},
year = {2025}
}