Energy Decomposition Analysis with a Stable Charge-Transfer Term for Interpreting Intermolecular Interactions.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Decomposing intermolecular interaction energies into physically meaningful components is crucial in quantum chemistry.
• Defining the charge-transfer (CT) contribution has been challenging, often showing strong basis set dependence.
• Accurate CT energy definition is vital for understanding dative bonding and open-shell complexes.

Purpose of the Study:

• To analyze charge-transfer (CT) interactions predicted by various energy decomposition analyses (EDAs).
• To recommend a robust and chemically intuitive definition for CT energy.
• To develop a reliable EDA method applicable to diverse supramolecular complexes.

Main Methods:

• Analysis of several popular energy decomposition analyses (EDAs) for CT interactions.
• Utilizing constrained density functional theory (cDFT) for defining the CT contribution.
• Employing symmetry-adapted perturbation theory (SAPT) for electrostatic, polarization, Pauli repulsion, and van der Waals contributions.

Main Results:

• Constrained density functional theory (cDFT) provides a CT definition with minimal basis set dependence.
• cDFT results align with chemical intuition and experimental estimates for CT energy.
• The combined SAPT/cDFT approach offers a stable and physically motivated energy decomposition.

Conclusions:

• The recommended SAPT/cDFT composite approach provides a stable and physically meaningful energy decomposition.
• cDFT is recommended for defining the CT component due to its basis set independence and chemical intuition.
• The new implementation of open-shell SAPT enables application to complexes involving molecules, ions, and radicals.