Electrostatic Potential-Based Method of Balancing Charge Transfer Across ONIOM QM:QM Boundaries

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• ONIOM hybrid calculations can contain errors due to unaddressed charge redistribution.
• Accurate prediction of reaction energies is crucial in computational chemistry.

Purpose of the Study:

• To develop a novel, cost-effective method to improve ONIOM calculations.
• To enhance the accuracy of reaction energies by accounting for charge-transfer effects.

Main Methods:

• A new method based on matching electrostatic potential (ESP) between model and real systems.
• Implementing an optimum one-electron potential in a buffer region to manage charge redistribution.
• Iterative optimization of link atom nuclear charge to match ESP distributions.

Main Results:

• The new ESP-ONIOM-CT method significantly improves accuracy by 40-60% over standard ONIOM.
• Optimized charges are small and align with physical intuition.
• The method is independent of arbitrary charge definitions and less basis set dependent.

Conclusions:

• ESP-ONIOM-CT offers a robust and physically grounded approach to enhance ONIOM calculations.
• This method provides a more accurate prediction of reaction energies, especially for systems with charge redistribution.
• The technique is versatile and can be extended to complex reactions with multiple link atoms.