Electronic coupling, the off-diagonal element of the diabatic Hamiltonian, plays a key role in determining the chemical dynamics in a variety of processes, ranging from hole and electron transfer reactions to excitation energy transfers. In this work, we assess DFT-based approaches for generating diabatic states and calculating electronic couplings, including the projection-operator diabatization, fragment-orbital DFT, constrained DFT, and multistate DFT methods. By benchmarking these methods on hole and electron transfer systems, we show that schemes based on fragment-orbital DFT overall yield the most accurate results, albeit at the cost of not providing variationally optimized diabatic wavefunctions and the possibility of resulting in spurious symmetry breaking. These shortcomings limit the generalizability of these methods and their use in real-time dynamics. In contrast, while we observe that constrained and multistate DFT-based approaches lead to less accurate results in general, they provide access to variationally optimized many-electron wavefunctions and the associated nuclear gradients, thereby permitting their use in guiding real-time dynamics. Finally, we suggest an approach that incorporates the beneficial features of fragment-orbital based methods and access to variationally optimized wavefunctions making use of absolutely localized molecular orbitals (ALMOs).

Accurate prediction of electronic coupling for hole and electron transfer problems using DFT-based approaches

2019 Fall National Meeting

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