Reorganization energy of electron transfer at the solvent glass transition

TL;DR

This study uses molecular dynamics to investigate how the solvent reorganization energy in supercooled water sharply decreases at the glass transition, indicating dynamical arrest of solvent relaxation processes.

Contribution

It provides the first detailed molecular-dynamics analysis linking solvent reorganization energy to the structural arrest at the water glass transition.

Findings

Reorganization energy sharply drops at the transition temperature.

Heat capacity and dielectric susceptibility show sharp drops at the same temperature.

Translational diffusion increases relative to rotational relaxation at the transition.

Abstract

We present a molecular-dynamics study of the solvent reorganization energy of electron transfer in supercooled water. We observe a sharp decrease of the reorganization energy at a temperature identified as the temperature of structural arrest due to cage effect as discussed by the mode coupling theory. Both the heat capacity and dielectric susceptibility of the pure water show sharp drops at about the same temperature. This temperature also marks the onset of the enhancement of translational diffusion relative to rotational relaxation signaling the break-down of the Stokes-Einstein relation. The change in the reorganization energy at the transition temperature reflects the dynamical arrest of the slow, collective relaxation of the solvent related to Debye relaxation of the solvent dipolar polarization.