Abstract
The FlexiBLE embedding method introduced in Paper I [Z. Shen and W. J. Glover, J. Chem. Phys. 155, 224112 (2021)] is applied to explore the structure and dynamics of the aqueous solvated electron at an all-electron density functional theory Quantum Mechanics/Molecular Mechanics level. Compared to a one-electron mixed quantum/classical description, we find the dynamics of the many-electron model of the hydrated electron exhibits enhanced coupling to water OH stretch modes. Natural bond orbital analysis reveals this coupling is due to significant population of water OH σ* orbitals, reaching 20%. Based on this, we develop a minimal frontier orbital picture of the hydrated electron involving a cavity orbital and important coupling to 4-5 coordinating OH σ* orbitals. Implications for the interpretation of the spectroscopy of this interesting species are discussed.
Highlights
Compared to a one-electron mixed quantum/classical description, we find the dynamics of the many-electron model of the hydrated electron exhibits enhanced coupling to water OH stretch modes
The hydrated electron, e−aq, an excess electron embedded in liquid water, is the quintessential system exhibiting solvent-supported electronic states, and has been used as an ideal probe of water’s solvation dynamics, since the electron itself has no internal degrees of freedom that might muddy a pump-probe spectrum
By performing Natural Bond Orbital (NBO) analysis, we show that this coupling arises from significant occupation of OH σ∗ antibonding orbitals, in a similar fashion to that observed in water anion clusters.[22]
Summary
The hydrated electron, e−aq, an excess electron embedded in liquid water, is the quintessential system exhibiting solvent-supported electronic states, and has been used as an ideal probe of water’s solvation dynamics, since the electron itself has no internal degrees of freedom that might muddy a pump-probe spectrum. To explore the influence of an excess electron on water’s electronic structure and dynamics, we performed many-electron FlexiBLE-QM/MM AIMD simulations at the BH&HLYP/6-31++G* level on a model of the condensed-phase e−(aq). By performing Natural Bond Orbital (NBO) analysis, we show that this coupling arises from significant occupation of OH σ∗ antibonding orbitals, in a similar fashion to that observed in water anion clusters.[22]. This allows us to develop a minimal frontier orbital description of e−(aq), involving a cavity orbital and strong coupling to 4-5 OH σ∗ orbitals.
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