A Simplified Treatment of Solvent-Solute Dispersion^†

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Solvation Theory

Background:

• The polarizable continuum model (PCM), specifically IEF-PCM, is widely used for electrostatic reaction fields.
• Standard PCM treats solvents as isotropic dielectrics, effective for charged solutes but less so for dispersion interactions in low-dielectric solvents.
• Accurate modeling of solvent-solute dispersion is crucial in low-dielectric media, particularly for nonpolar solutes.

Purpose of the Study:

• To optimize the universal dispersion coefficient (cf⁽⁶⁾) used in PCM calculations.
• To enhance the accuracy of solvation energy predictions, especially in low-dielectric-constant solvents.
• To improve the modeling of dispersion interactions between solutes and solvents.

Main Methods:

• Optimization of the Caillet-Claverie dispersion coefficient (cf⁽⁶⁾) against 1031 experimental solvation energies from the SMSSP dataset.
• Utilized 29 low-dielectric-constant solvents for parameterization.
• Applied the refined cf⁽⁶⁾ value to calculate solvation energies for a new set of 61 solvents (1054 data points).

Main Results:

• An optimized dispersion coefficient of cf⁽⁶⁾ = 0.1650 kcal mol^-1 was determined, differing from the conventional value of 0.2140 kcal mol^-1.
• The refined parameter demonstrated a substantial improvement in the accuracy of calculated solvation energies.
• The improved model showed better performance for solvents containing large electronegative atoms.

Conclusions:

• The optimized dispersion coefficient significantly enhances the accuracy of PCM solvation energy calculations, particularly in low-dielectric solvents.
• This refinement addresses the underestimation of dispersion interactions in previous models.
• The study provides a more reliable computational tool for predicting solvation energies across a wider range of solvent types.