Quantum chemistry in solution by combining 3D integral equation theory with a cluster embedding approach

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Theoretical Chemistry

Background:

• Predicting free energy changes in solution is crucial for understanding chemical reactions.
• Integral equation theory and quantum chemistry are established methods for such calculations.
• Existing methods often require empirical parameterization, limiting their general applicability.

Purpose of the Study:

• To develop and validate a novel computational method for accurate prediction of chemical reaction free energies in solution.
• To assess the performance of the embedded cluster-reference interaction site model (EC-RISM) approach.
• To apply the EC-RISM method to benchmark chemical systems without empirical parameter adjustments.

Main Methods:

• Utilizing 3D reference interaction site model (RISM) integral equation theory.
• Integrating RISM with quantum-chemical calculations through an embedded cluster (EC) approach.
• Self-consistently computing solute electronic structure and solvent structure by mapping solvent charge distribution onto background point charges.

Main Results:

• The EC-RISM procedure achieved chemical accuracy in free energy predictions across several benchmark systems.
• No empirical parameters were required for the EC-RISM method.
• Successful application to the gauche-trans equilibrium of 1,2-dichloroethane and pKa shifts of acids/anilines in water.

Conclusions:

• The EC-RISM method offers a computationally efficient and accurate approach for calculating solution-phase reaction free energies.
• This method provides a parameter-free route to achieve high accuracy in theoretical chemistry predictions.
• EC-RISM is a promising tool for studying chemical equilibria and acid-base properties in aqueous solutions.