Improved Projection-Operator Diabatization Schemes for the Calculation of Electronic Coupling Values

Area of Science:

• Quantum Chemistry
• Computational Materials Science

Background:

• The projection-operator diabatization method is crucial for calculating charge transfer couplings in donor-acceptor systems.
• Existing methods suffer from non-localized diabats due to basis-set orthogonalization, leading to underestimated coupling strengths and basis set dependency.

Purpose of the Study:

• To resolve the ambiguity in DFT-based projection-operator diabatization for charge transfer couplings.
• To develop a reformulated method that yields localized diabats and improves basis set convergence.

Main Methods:

• Reformulation of the projection-operator diabatization method within a tight-binding model.
• Ensuring diabat orthogonality using symmetric Löwdin or asymmetric Gram-Schmid procedures.
• Testing the improved method on the Hab11 benchmark set.

Main Results:

• The reformulated method generates diabats with increased localization.
• Achieved proper basis set convergence, reducing spurious dependence on basis set choice.
• Demonstrated improved performance for the Hab11 benchmark set, yielding more accurate coupling strengths.

Conclusions:

• The revised diabatization method provides a more accurate and reliable approach for charge transfer coupling calculations.
• The use of asymmetric Gram-Schmid procedures extends applicability to asymmetric systems like surface adsorbates.