A one-electron model for the aqueous electron that includes many-body electron-water polarization: Bulk equilibrium structure, vertical electron binding energy, and optical absorption spectrum

Abstract

Previously, we reported an electron-water pseudopotential designed to be used in conjunction with a polarizable water model, in order to describe the hydrated electron [L. D. Jacobson et al., J. Chem. Phys. 130, 124115 (2009)]. Subsequently, we found this model to be inadequate for the aqueous electron in bulk water, and here we report a reparametrization of the model. Unlike the previous model, the current version is not fit directly to any observables; rather, we use an ab initio exchange-correlation potential, along with a repulsive potential that is fit to reproduce the density maximum of the excess electron's wave function within the static-exchange approximation. The new parametrization performs at least as well as the previous model, as compared to ab initio benchmarks for (H(2)O)(n) (-) clusters, and also predicts reasonable values for the diffusion coefficient, radius of gyration, and absorption maximum of the bulk species. The new model predicts a vertical electron binding energy of 3.7 eV in bulk water, which is 1.4 eV smaller than the value obtained using nonpolarizable models; the difference represents the solvent's electronic reorganization energy following electron detachment. We find that the electron's first solvation shell is quite loose, which may be responsible for the electron's large, positive entropy of hydration. Many-body polarization alters the electronic absorption line shape in a qualitative way, giving rise to a high-energy tail that is observed experimentally but is absent in previous simulations. In our model, this feature arises from spatially diffuse excited states that are bound only by electronic reorganization (i.e., solvent polarization) following electronic excitation.

Hydration dynamics in water clusters via quantum molecular dynamics simulations

“…18,39,53,57,58,59,60,61 The TuriBorgis (TB) model 53 used in the present study has provided a consistent microscopic picture and a semi-quantitative agreement with experiment. 22,43,53,62,63,64 .…”

“…This is the main motivation for using the TB potential in the present study. Two other models have been proposed more recently, the one by the Herbert group, 61 the other by Schwartz and his co-workers. 39 The Jacobson-Herbert (JH) model employs a polarizable water potential and rigid water molecules providing good agreement with experiment and moderately high-level ab initio calculations.…”

“…39 The Jacobson-Herbert (JH) model employs a polarizable water potential and rigid water molecules providing good agreement with experiment and moderately high-level ab initio calculations. 61 The TB and the JH potentials predict cavity model for the bulk hydrated electron. 53,61 The Larsen-Glover-Schwartz (LGS) potential 39 is based on a one-electron frozen-core pseudopotential theory 59,65 similar to the TB model.…”

“…61 The TB and the JH potentials predict cavity model for the bulk hydrated electron. 53,61 The Larsen-Glover-Schwartz (LGS) potential 39 is based on a one-electron frozen-core pseudopotential theory 59,65 similar to the TB model. 66 Due to its different parametrization the…”

Embedded Cluster Models for Reactivity of the Hydrated Electron

“…The closer match between the bulk simulations 6 , when compared to the ab initio simulations, as well as to most of the one-electron pseudopotentials in the aqueous bulk. The coordination number of water molecules in the first solvent shell as calculated with the above methodologies is typically about four [43][44][45]. The first peak of the radial distribution of oxygen atoms around the center of the spin density from the AIMD simulations is located at 2.5 Å, while the corresponding distance of the oxygen atoms of all water molecules is 2.8 Å for e − (H 2 O) 4 and 3.0 Å for e − (H 2 O) 6 .…”