Accuracy of Discrete-Continuum Solvation Model for Cations: A Benchmark Study

Area of Science:

• Computational chemistry
• Physical chemistry
• Biochemistry

Background:

• Accurate modeling of ion solvation is essential for various scientific disciplines.
• Existing models include explicit, continuum, and hybrid discrete-continuum approaches.
• The discrete-continuum model balances accuracy and computational cost by treating the first solvation shell explicitly and the bulk solvent as a continuum.

Purpose of the Study:

• To systematically benchmark the discrete-continuum solvation model for cations with +2, +3, and +4 charges.
• To compare the model's performance against the SMD continuum model and experimental data.
• To evaluate the model's ability to reproduce known trends in ion solvation.

Main Methods:

• Calculated hydration free energies (HFEs) for various cations using the discrete-continuum model.
• Compared calculated HFEs with results from the SMD continuum model.
• Validated results against available experimental hydration free energy data.

Main Results:

• The discrete-continuum model demonstrated improved accuracy and consistency over the SMD continuum model alone.
• The model generally reproduced established trends, such as the Irving-Williams series.
• Lanthanide (Ln³⁺) ions presented challenges, exhibiting greater error and difficulty in reproducing HFE trends.

Conclusions:

• The discrete-continuum model is a recommended approach for calculating cation hydration free energies, especially when experimental data is lacking.
• The model provides a favorable balance between computational efficiency and predictive accuracy.
• Specific ion types, like Ln³⁺, may require further refinement of solvation models.