Electron hydration dynamics in water clusters: A direct ab initio molecular dynamics approach

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• Understanding electron attachment dynamics is crucial for solvation processes.
• Water clusters provide a simplified model for studying electron-solvation interactions.
• Previous studies lacked detailed insights into the initial stages of electron capture in small water clusters.

Purpose of the Study:

• To investigate the full-dimensional electron attachment dynamics in water clusters (H2O)n, for n=2 and 3.
• To elucidate the initial processes of electron hydration and structural changes.
• To determine the time scales of electron localization and hydrogen bond breaking.

Main Methods:

• Employed a direct ab initio molecular dynamics (MD) simulation.
• Utilized the MP2/6-311++G(d,p) level of theory for electronic structure calculations.
• Simulated electron attachment dynamics in water clusters (H2O)2 and (H2O)3.

Main Results:

• In (H2O)3, excess electron capture initially traps around a cyclic trimer, followed by localization into two, then one water molecule.
• Hydrogen bond breaking occurs within 100-300 fs, driven by the excess electron, leading to a linear structure.
• A dipole-bound state is formed in (H2O)3 after structural rearrangement; in (H2O)2, a dipole-bound anion forms directly.

Conclusions:

• Direct ab initio MD simulations successfully visualized the initial hydration process of excess electrons in water clusters.
• Hydrogen bond breaking is a key early event in electron capture by water trimers.
• The study provides critical insights into the mechanism of electron hydration dynamics at the molecular level.