Weighted-density functionals for cavity formation and dispersion energies in continuum solvation models

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Continuum solvation models are crucial for first principles calculations of chemical reactions in solution.
• Current models necessitate extensive parametrization for each solvent and solute system, limiting their applicability.
• Empirical terms in existing models hinder accuracy and broad usability.

Purpose of the Study:

• To develop a minimally-empirical solvation model by replacing empirical terms with physically derived components.
• To enhance the efficiency and accuracy of predicting solvation energies for chemical reactions.
• To reduce the reliance on extensive experimental data for model parametrization.

Main Methods:

• Derived solvent radii from ab initio calculations of nonlocal dielectric response.
• Developed a parameter-free weighted-density approximation for cavity formation free energy.
• Utilized a pair-potential approximation for dispersion energy calculations.
• Introduced a single solvent-independent parameter (electron density threshold, nc) and a single solvent-dependent parameter (dispersion scale factor, s6).

Main Results:

• The model accurately reproduced solvation energies for organic molecules in water, chloroform, and carbon tetrachloride with low RMS errors (1.1, 0.6, and 0.5 kcal/mol, respectively).
• Fitting the solvent-dependent parameter (s6) to a single non-polar molecule's solvation energy minimally impacted accuracy.
• Demonstrated that parametrization for new solvents requires minimal effort and no extensive experimental databases.

Conclusions:

• The developed minimally-empirical solvation model offers a significant improvement over existing methods.
• The model's reduced parametrization requirements make it highly adaptable to various solvents and solute systems.
• This approach facilitates more efficient and accurate first principles calculations of chemical processes in solution.