Single and Double Excess Electrons in Water Clusters (original) (raw)
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Surface states of excess electrons on water clusters
Physical Review Letters, 1987
Electron attachment of water clusters was explored by the quantum path-integral molecular-dynamics method, demonstrating that the energetically favored localization mode involves a surface state of the excess electron. The cluster size dependence, the energetics, and the charge distribution of these novel electron-cluster surface states are explored.
Electron Localization in Water Clusters
The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 1987
Electron attachment to water clusters was explored by the quantum path integral molecular dynamics method, demonstrating that the energetically favored localization mode involves a surf ice state of the excess electron , rather than the precursor of the hydra ted electron. The clus ter size dependence, the energetics and the charge.distribution of these novel electron-cluster surface states axe explored. I.
The Hydrated Electron as a Pseudo-Atom in Cavity-Bound Water Clusters
Journal of Chemical Theory and Computation, 2007
Anionic water clusters, (H 2 O) n -, of various sizes, n ) 1-8, have been investigated using high-level ab initio calculations and the quantum theory of atoms in molecules, which provides a topological analysis of the electron density. The results of the current study indicate that the distribution of the excess electron is dependent on the geometry of the cluster. Nonnuclear attractors (NNAs), with associated pseudo-atomic basins and populations, are observed only in the highly symmetric clusters in which several non-hydrogen-bonded (NHB) hydrogen atoms are oriented toward a central cavity. For the latter cases, the non-nuclear attractor can be considered a pseudo-atom, possessing a significant portion of the excess electron within the cavity, consistent with the cavity-bound model of the solvated electron. In some cases, the population of the NNA is more than 0.2 electrons, and it contributes in excess of 20 kJ/mol to the energy of the system. Furthermore, the less symmetric systems, which tend to orient the NHB hydrogen atoms away from the center of the cluster, tend to delocalize the excess electron to a greater extent over several atoms at the surface of the cluster, consistent with the surfacebound model of the excess electron.
Size dependence of the energetics of electron attachment to large water clusters
Chemical Physics Letters, 1988
The size dependence of the binding energy of a localized excess electron in large water clusters originates from long-range polarization interactions. The vertical and adiabatic binding energies of compact, interior excess electron states in (H20); clusters, obtained from quantum path-integral moleculardynamics simulations, exhibit a linear dependence on n -I/', in quantitative agreement with the implications of dielectric medium effects in finite systems.
Chemical physics letters, 2006
Green's function (GF) calculations for the valence electron binding energies of water clusters (H2O)(2-8) are reported. The results are compared with experiment for H2O and (H2O)(2), and with Hartree-Fock and Kohn-Sham calculations with an exchange-correlation functional parametrized to reproduce electronic properties of the dimer. For the liquid, sequential Monte Carlo/GF calculations lead to estimates of the outermost electron binding energy (11.59 +/- 0.12eV) and of the water conduction band edge (V-0) as -0.79 +/- 0.08 eV. Our predictions agree with experimental and recent theoretical results and support that the water electron affinity (-V-0) is smaller than the typical literature value (1.2 eV).
Relaxation Dynamics and Genuine Properties of the Solvated Electron in Neutral Water Clusters
The Journal of Physical Chemistry Letters, 2019
We have investigated the solvation dynamics and the genuine binding energy and photoemission anisotropy of the solvated electron in neutral water clusters with a combination of time-resolved photoelectron velocity map imaging and electron scattering simulations. The dynamics was probed with a UV probe pulse following above-band-gap excitation by an EUV pump pulse. The solvation dynamics is completed within about 2 ps. Only a single band is observed in the spectra, with no indication for isomers with distinct binding energies. Data analysis with an electron scattering model reveals a genuine binding energy in the range of 3.55−3.85 eV and a genuine anisotropy parameter in the range of 0.51−0.66 for the ground-state hydrated electron. All of these observations coincide with those for liquid bulk, which is rather unexpected for an average cluster size of 300 molecules.
The electronic structure of free water clusters probed by Auger electron spectroscopy
Chemical Physics, 2005
͑H 2 O͒ N clusters generated in a supersonic expansion source with N ϳ 1000 were core ionized by synchrotron radiation, giving rise to core-level photoelectron and Auger electron spectra ͑AES͒, free from charging effects. The AES is interpreted as being intermediate between the molecular and solid water spectra showing broadened bands as well as a significant shoulder at high kinetic energy. Qualitative considerations as well as ab initio calculations explain this shoulder to be due to delocalized final states in which the two valence holes are mostly located at different water molecules. The ab initio calculations show that valence hole configurations with both valence holes at the core-ionized water molecule are admixed to these final states and give rise to their intensity in the AES. Density-functional investigations of model systems for the doubly ionized final statesthe water dimer and a 20-molecule water cluster-were performed to analyze the localization of the two valence holes in the electronic ground states. Whereas these holes are preferentially located at the same water molecule in the dimer, they are delocalized in the cluster showing a preference of the holes for surface molecules. The calculated double-ionization potential of the cluster ͑22.1 eV͒ is in reasonable agreement with the low-energy limit of the delocalized hole shoulder in the AES.
Excess Electron in Water at Different Thermodynamic Conditions
A hydrated electron in water at different densities and temperatures is studied via a set of density functional based molecular dynamics simulations, showing that a localization of an excess electron is still present even at very low densities. Space variations of the molecular dipole moments are analyzed, proposing a simple algorithm to identify the region of localization of the wavefunction relative to the solvated electron in terms of orientation of the H2O molecular dipole moments. Finally, the effects of the self-interaction corrections on the optical absorption spectra are analyzed and compared with both available experimental data and path integral molecular dynamics calculations, showing that a weighted subtraction of the self-interaction yields a systematic improvement in the position of the absorption peak.
The Journal of Chemical Physics, 1992
The energetics, structure, and stability of a dielectron solvated in an internal cavity in water clusters, ( H, 0); *, at 300 K are investigated using coupled quantum-classical moleculardynamics simulations. In these calculations the ground state of the dielectron is calculated concurrently with the atomic configurations using the local-spin-density functional method, and the nuclear degrees of freedom evolve classically on the Born-Oppenheimer potentialenergy surface. For n = 64 and 128 the internal single-cavity dielectron state is unstable, while for n = 256 (as well as in bulk water) it is energetically stable, fluctuating between a compact spherical configuration (eZ, ) and an elongated ellipsoidal dumbbell-shaped one ( e2d ) . Transitions between these two states of the dielectron are accompanied by structural and orientational transformations of the surrounding water molecules. The induced molecular orientational order is enhanced and is of longer range in (H, O)$ than is the case for a solvated single excess electron. By extrapolating our results to the bulk limit we conclude that a spin-paired dielectron state in bulk water, at 300 K, is a stable species relative to two single separated hydrated electrons.
Quantum chemical and electrostatic studies of anionic water clusters
Journal of Molecular Structure: THEOCHEM, 2008
Quantum chemical investigations are carried out to determine the structure and energetics of anionic water clusters, (H2O)n- for n=8,10,12 and 15. Quantum chemical computations performed herein employing a density functional theory (DFT) prescription reveal that these open-shell anionic clusters are metastable in comparison with their neutral analogues. Electron localization of the excess electron in these clusters, traced through molecular electrostatic potential (MESP) and singly occupied molecular orbital (SOMO) density maps, brings out the fact that the excess electron in these clusters is essentially a ‘surface’ electron i.e. binds externally to the cluster.