A classical model for three-body interactions in aqueous ionic systems.

Area of Science:

• Computational chemistry
• Physical chemistry
• Molecular modeling

Background:

• Accurate modeling of aqueous ionic systems is crucial for understanding chemical and biological processes.
• Existing many-body force fields often require extensive ion-specific parameterization.
• Three-body interactions significantly influence the properties of ionic solutions.

Purpose of the Study:

• To develop and validate a classical induction model for three-body ion-water-water (I-W-W) and water-water-water (W-W-W) interactions.
• To assess the model's accuracy against high-level quantum mechanical calculations.
• To provide a transferable and efficient method for modeling aqueous ionic systems.

Main Methods:

• Developed a classical induction model using distributed multipoles and polarizabilities for water and ions.
• Employed electrostatic interactions up to hexadecapole and polarizabilities up to quadrupole-quadrupole.
• Benchmarked the model against reference three-body energies from Moller-Plesset perturbation theory and coupled-cluster calculations.

Main Results:

• The classical model demonstrated excellent agreement with reference CCSD(T) three-body energies.
• Achieved low Root-Mean-Square-Errors (RMSEs) for monatomic cations (0.29 kcal/mol), anions (0.25 kcal/mol), and polyatomic ions (0.12 kcal/mol).
• The model's RMSE for W-W-W interactions was 0.12 kcal/mol, comparable to MB-pol training data.

Conclusions:

• The proposed classical induction model accurately captures three-body interactions in aqueous ionic systems.
• This approach offers a fast, efficient, and transferable alternative to computationally expensive ab initio methods.
• The model facilitates the extension of many-body force fields for diverse ionic solutions without ion-specific fitting.