Structure and energetics of the hydronium hydration shells

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Biophysical Chemistry

Background:

• Proton solvation and mobility are crucial in chemical and biological systems.
• Understanding the behavior of hydronium ions (H3O+) in water is fundamental.
• Existing models require refinement to accurately describe proton hydration shells.

Purpose of the Study:

• To investigate the hydration shells of H3O+ across a temperature range (260–340 K).
• To calculate radial distribution functions for protonium and its solvation shells.
• To determine thermodynamic properties (Gibbs energy, enthalpy) of hydrogen bonds in solvation shells compared to bulk water.

Main Methods:

• Multistate empirical valence bond (MS-EVB2) methodology.
• Calculation of radial distribution functions.
• Thermodynamic analysis of hydrogen bond energies.

Main Results:

• Systematic differences in hydrogen bond energies were observed between the first two solvation shells of H3O+ and bulk water.
• Calculated bond energies align with recent infrared spectroscopy studies on proton hydration.
• Quantified Gibbs energy and enthalpy changes for hydrogen bond donation/acceptance.

Conclusions:

• The study provides detailed insights into the structure and energetics of H3O+ hydration shells.
• Observed bond-energy differences have significant implications for understanding proton mobility mechanisms.
• Results contribute to a more accurate molecular-level understanding of proton transfer in aqueous environments.