  Density functional theory (DFT) is used to rationalize magnetic parameters of
hydrated electron trapped in alkaline glasses as observed using Electron
Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM)
spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24)
that localize the electron internally are examined. It is shown that EPR
parameters of such water anions (such as hyperfine coupling tensors of H/D
nuclei in the water molecules) are defined mainly by the cavity size and the
coordination number of the electron; the water molecules in the second
solvation shell play a relatively minor role. An idealized model of hydrated
electron (that is usually attributed to L. Kevan) in which six hydroxyl groups
arranged in an octahedral pattern point towards the common center is shown to
provide the closest match to the experimental parameters, such as isotropic and
anisotropic hyperfine coupling constants for the protons (estimated from
ESEEM), the second moment of the EPR spectra, and the radius of gyration. The
salient feature of these DFT models is the significant transfer (10-20%) of
spin density into the frontal O 2p orbitals of water molecules. Spin bond
polarization involving these oxygen orbitals accounts for small, negative
hyperfine coupling constants for protons in hydroxyl groups that form the
electron-trapping cavity. In Part 2, these results are generalized for more
realistic geometries of core anions obtained using a dynamic one-electron mixed
qunatum/classical molecular dynamics model.
