Hydration of ionic species studied by the reference interaction site model with a repulsive bridge correction

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Physical Chemistry

Background:

• Accurate prediction of ionic hydration energies is crucial for understanding chemical processes.
• Existing models often struggle with precise calculations for polyatomic ions and complex solvation effects.
• The reference interaction site model (RISM) offers a framework for studying solvation, but requires robust closure relations and corrections.

Purpose of the Study:

• To evaluate the performance of the RISM theory combined with hypernetted chain (HNC) and partially linearized hypernetted chain (PLHNC) closures, augmented by a repulsive bridge correction (RBC).
• To analyze the decomposition of hydration energies into electrostatic and nonpolar components, and their enthalpic contributions.
• To investigate the impact of the repulsive bridge correction on the electrostatic potential experienced by solute atoms.

Main Methods:

• Application of the reference interaction site model (RISM) with HNC and PLHNC closure approximations.
• Incorporation of a repulsive bridge correction (RBC) treated as a thermodynamic perturbation.
• Analysis of hydration energies (electrostatic and nonpolar) and enthalpic contributions for diverse ionic species.

Main Results:

• The RISM/HNC+RBC and RISM/PLHNC+RBC models yield hydration energies with deviations of only a few percent from experimental values for atomic and molecular ions.
• Enthalpic contributions to free energies are also found to be in close agreement with experimental data.
• The models successfully predict electrostatic potentials around ionic species and provide qualitative estimates of Samoilov activation energies for univalent atomic ions.

Conclusions:

• The RISM theory, enhanced with HNC/PLHNC closures and RBC, provides a reliable and accurate method for calculating hydration energies and related properties of ionic species.
• The repulsive bridge correction significantly improves the accuracy of the RISM model, particularly for electrostatic interactions and enthalpic contributions.
• These advanced RISM models offer a valuable tool for theoretical investigations in solution chemistry and solvation thermodynamics.