The Hydrated Electron as a Pseudo-Atom in Cavity-Bound Water Clusters

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• Anionic water clusters ((H2O)n(-)) are fundamental units for understanding the behavior of excess electrons in aqueous environments.
• The distribution and localization of excess electrons significantly influence the properties of these clusters.

Purpose of the Study:

• To investigate the geometric dependence of excess electron distribution in anionic water clusters (n=1-8).
• To analyze the topological properties of electron density using the Quantum Theory of Atoms in Molecules (QTAIM).

Main Methods:

• High-level ab initio calculations were employed to model anionic water clusters.
• Quantum Theory of Atoms in Molecules (QTAIM) was used for topological analysis of electron density.
• Analysis focused on the presence and properties of non-nuclear attractors (NNAs).

Main Results:

• Excess electron distribution is strongly dependent on cluster geometry.
• Non-nuclear attractors (NNAs), representing localized excess electrons, were observed in highly symmetric clusters with central cavities.
• Less symmetric clusters showed delocalization of the excess electron over surface atoms.

Conclusions:

• The study supports both cavity-bound and surface-bound models for solvated electrons based on cluster symmetry.
• NNAs can act as pseudo-atoms, significantly contributing to the cluster's energy.
• Geometric arrangement of non-hydrogen-bonded hydrogen atoms dictates electron localization.