Accurate and efficient DFT-based diabatization for hole and electron transfer using absolutely localized molecular orbitals

TL;DR

This paper introduces a new DFT-based diabatization method using absolutely localized molecular orbitals (ALMOs) that accurately computes diabatic couplings for electron and hole transfer processes, applicable to complex molecular systems.

Contribution

The authors develop a novel ALMO-based approach with symmetrized transition density matrices for improved diabatic coupling calculations, compatible with various DFT levels.

Findings

Accurate diabatic couplings across diverse molecular systems.

Enhanced method performance with lower-tier DFT calculations.

Compatibility with quantum dynamics for nonadiabatic processes.

Abstract

Diabatic states and the couplings between them are important for quantifying, elucidating, and predicting the rates and mechanisms of many chemical and biochemical processes. Here, we propose and investigate approaches to accurately compute diabatic couplings from density functional theory (DFT) using absolutely localized molecular orbitals (ALMOs). ALMOs provide an appealing approach to generate variationally optimized diabatic states and obtain their associated forces that allows for the relaxation of the donor and acceptor orbitals in a way that is internally consistent in how the method treats both the donor and acceptor states. Here, we show that one can obtain more accurate electronic couplings between ALMO-based diabats by employing the symmetrized transition density matrix to evaluate the exchange-correlation contribution. We demonstrate that this approach yields accurate results in comparison to other commonly used DFT-based diabatization methods across a wide array of electron and hole transfer processes occurring in systems ranging from conjugated organic molecules, such as thiophene and pentacene, to DNA base pairs. We also show that this approach yields accurate diabatic couplings even when combined with lower tiers of the DFT hierarchy, opening the door to combining it with quantum dynamics approaches to provide an ab initio treatment of nonadiabatic processes in the condensed phase.