The initial and final states of electron and energy transfer processes: Diabatization as motivated by system-solvent interactions

Abstract

For a system which undergoes electron or energy transfer in a polar solvent, we define the diabatic states to be the initial and final states of the system, before and after the nonequilibrium transfer process. We consider two models for the system-solvent interactions: A solvent which is linearly polarized in space and a solvent which responds linearly to the system. From these models, we derive two new schemes for obtaining diabatic states from ab initio calculations of the isolated system in the absence of solvent. These algorithms resemble standard approaches for orbital localization, namely, the Boys and Edmiston-Ruedenberg ͑ER͒ formalisms. We show that Boys localization is appropriate for describing electron transfer ͓Subotnik et al., J. Chem. Phys. 129, 244101 ͑2008͔͒ while ER describes both electron and energy transfer. Neither the Boys nor the ER methods require definitions of donor or acceptor fragments and both are computationally inexpensive. We investigate one chemical example, the case of oligomethylphenyl-3, and we provide attachment/detachment plots whereby the ER diabatic states are seen to have localized electron-hole pairs.

Exciton delocalization, charge transfer, and electronic coupling for singlet excitation energy transfer between stacked nucleobases in DNA: An MS-CASPT2 study

“…An interesting question is the relation between the dynamic diabatic states ψ i and ψ j which minimize the coupling ψ i |∇ R |ψ j and the "chemical" diabatic states corresponding to initial and final states in electron or exciton transfer processes and (almost) completely localized on the donor and acceptor states. This issue was considered in detail by Pavanello and Neugebauer 36 and Subbotnik et al 37,38 and will not be addressed in the present paper.…”

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

“…In particular, Q-CHEM now allows the user to transform CIS or TDDFT/TDA adiabatic excited states according to either Boys [353] or EdmistonRuedenberg [354] localised diabatisation. Diabatic states {| I > } can be generated from multiple (N states ≥ 2) adiabatic states…”

Optimal diabatic bases via thermodynamic bounds

“…In comparison to previous methods that define diabats for kinetic problems such as energy and electron transfer, the thermodynamic criterion has the advantage of being more general -for example, in General-ized Mulliken-Hush, [10] a specific operator is introduced for obtaining charge-transfer states appropriate for electron transfer rates. An alternative prescription, [11] using localization criteria, provides states appropriate for energy-transfer. The thermodynamic criteria can be used in both electron and energy transfer regimes by modifying the system-bath interaction.…”

“…The first problem suggests an expansion of diabatic states in an adiabatic basis; the goal is then to determine the adiabaticdiabatic transformation matrix by imposing some criterion for diabatic states, leading to methods such as fragment charge difference, [7] fragment excitation difference, [8,9] Generalized Mulliken-Hush, [10] and state localization. [4,11,12] Alternatively, diabatic states can be produced directly using either constraints on the electronic density [5,13] or valence bond wavefunctions. [14] Both deductive and constructive strategies, however, rely on a somewhat arbitrary set of criteria for diabatization, based on chemical intuition.…”