Fig. 1. Geometric diagram identifying terms in the Lie–Clementi dynamical potentials used in this work. As an example, r₁₃ in Eq. (5) is the distance between H(1) and H(3). The lengths R₁, R₂ and the angle θ define two OH bond lengths and a H–O–H bond, respectively. The corresponding equilibrium bond length R_e and angle θ_e are 0.9576 Å and 104.59°, respectively. There is a charge q on each H atom and a charge −2q at each site M. M is chosen to lie on the bisection line connecting O and the center of the H–H line. The ratio of OM distance to the bisection line length is fixed to be 0.457.

Fig. 2. Room temperature dynamical simulation of 112 pseudowater molecules and an excess electron in a cubic super-cell at (a) 0 fs, (b) 50 fs, and (c) 2 ps after a 3 ps effective equilibration. Right panels are enlargements of the first shell cavity structures. The excess electron charge distribution is shown in red and the six green water molecules identify the initial TR hexamer structure. The solid lines represent hydrogen bondings among the water molecules that comprise each cavity. In (b) the dashed line indicates the formation of a weak hydrogen bond as a new water molecule becomes part of the first shell.

Fig. 3. Spectral densities (power spectra) of oxygen velocity auto-correlation functions for a neutral system (top panel) and for a system with an excess electron (bottom panel). Spectral densities are defined by the formula, . In both cases, the blue (red) curves correspond to the first (second) time interval of 150 fs relaxation from an initial TR hexamer structure. The green curve is the equilibrium spectral density of bulk water.

Fig. 4. Spectral densities (power spectra) of hydrogen velocity auto-correlation functions for six water molecules which comprised a Kevan-like structure surrounding an excess electron at 1.4 ps (red) and for bulk equilibrated water (blue). To obtain the sepctral densities, the same formula as in Fig. 3 is used. The red curve is calculated after 1.4 ps run. The frequency, which shows a dramatic increase in red curve, corresponds to the H–O–H bending modes of water molecules.

Fig. 5. Mean square displacement of center of charge as a function of time for an excess electron in water. In order to ensure proper equilibrium of the excess electron, the mean square displacement is calculated using the final psec data of the 2 ps run described in the text. The configuration averaging was performed over 500 fs for each time point plotted in the figure. The dashed line represents a linear fit of Δr²6Dt that provides a diffusion constant of 5.0×10⁻⁵ cm²/s.

Fig. 6. Room temperature ab initio dynamical simulation of 106 pseudowater molecules, 12 hydrogen atoms, 6 oxygen atoms, and an excess electron in a cubic super-cell at (a) 20, (b) 40, and (c) 60 fs after a 2 ps effective equilibration. The excess electron charge distribution is shown in red and the six water molecules described by ionic pseudopotentials are tagged in green. Note how the electron moves to the right in a time-interval of 40 fs.

Table 1. Parameter values for molecular pseudopotentials

Table 2. Parameter values for intra- and intermolecular potentials. Values are taken from [22]