Diagonalizing the Hamiltonian in Table II yields a lowest eigenvalue of -1.08 eV, which while higher than the true average SOMO energy of -2.6 eV, shows that our simple model captures most of the stabilization of the cavity orbital by strongly coupling to four σ * OH orbitals (see Fig. for convergence of the eigenvalue with number of included σ * OH orbitals and Fig. for its correlation with the SOMO energy). The energy levels of the NBOs and model Hamiltonian eigenvalues are summarized in the MO diagram presented in Fig. . We notice an interesting stabilization of the most populated σ * 1 orbital's energy of ∼0.9 eV relative to the other σ * OH orbitals, that all have average energies of ∼14.2 eV. We found this stabilization arises due to a lengthening of the closest OH bond to the electron, which had an average length of 0.999±0.002 Å compared to the remaining QM OH bonds which had an average length of 0.9761±0.0003 Å. σ * 2 is stabilized by ∼0.3 eV in a similar manner, but to a lesser degree. Similar OH bond-length extensions were observed in the zero-Kelvin minimal cluster with polarizable continuum model put forward by Sevilla and co-workers. Thus, the partial occupation of water σ * OH orbitals is seen to noticeably weaken the coordinating OH bonds, which lowers the σ * OH orbital energies and further enhances their coupling to the excess electron. This physics is missed entirely by MQC models, and provides an explanation for the significant differences in e - (aq) 's dynamics we observe at the MQC and QM/MM levels.