Ab initio effective one-electron potential operators: Applications for charge-transfer energy in effective fragment...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Effective one-electron potentials (EOPs) are crucial for describing electronic structures in chemical systems.
• Fragment-based methods, like the effective fragment potentials (EFP2), are vital for studying large molecular aggregates.
• Electron repulsion integrals pose a significant computational challenge in these calculations.

Purpose of the Study:

• To develop a general method for eliminating electron repulsion integrals using EOPs.
• To adapt EOPs for fragment-based calculation methodologies, specifically the EFP2 method.
• To reduce the computational cost associated with charge-transfer (CT) terms in EFP2 potentials.

Main Methods:

• A general EOP-based method for eliminating electron repulsion integrals was developed.
• Two types of EOP operator matrix elements were treated using distributed multipole expansion and extended density fitting (DF).
• An alternative EOP-based CT energy model was derived within intermolecular perturbation theory.

Main Results:

• The EOP technique was applied to reduce the computational cost of EFP2 charge-transfer (CT) terms.
• The EOP-based CT energy model was found to be compatible with the original EFP2 formulation.
• Computational cost for EFP2 total interaction energy calculations decreased by up to 38 times.

Conclusions:

• The EOP-based formulation significantly enhances the efficiency of EFP2 calculations.
• The proposed model maintains accuracy for weakly interacting neutral and ionic molecular fragments.
• This method offers a computationally efficient and accurate approach for routine use within the EFP2 framework.