Spin-Flip TDDFT for Photochemistry

Herbert, John M.; Mandal, Aniket

doi:10.26434/chemrxiv-2022-gj75d

Cited by 6 publications

(11 citation statements)

References 119 publications

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“…That formalism, which is closely connected to response theory for optical properties, 141 is not discussed here but can be found elsewhere. 19,125,[142][143][144][145] Nonadiabatic or "derivative coupling" vectors between excited states, 27,146 which are needed for nonadiabatic molecular dynamics simulations, [23][24][25][26][27] have also been formulated. [147][148][149][150][151][152][153][154] Evaluation of the nonadiabatic couplings has the same formal complexity as evaluation of the excited-state gradient.…”

Section: Analytic Gradientsmentioning

confidence: 99%

“…146,325 The TDHF method suffers from the same deficiency, which is not a DFT artifact per se but rather a LR artifact, arising from an unbalanced description of the ground (reference) state and the excited (response) states. 27 The result is that the branching space around a conical seam that involves the two lowest electronic states is necessarily one-dimensional rather than two-dimensional. (For examples, see Refs.…”

Section: Conical Intersectionsmentioning

confidence: 99%

“…Even the CIS method can exhibit erratic behavior when the ground state becomes quasi-degenerate with the first excited state, 26,147 because in the absence of double excitations the ground-and excited-state eigenvalue problems are decoupled (according to Brillouin's theorem), 59 leading to an unbalanced description. 27,325 This is not a problem for conical intersections between two excited states because those states are coupled by the matrix A, in both CIS and LR-TDDFT. An example of a conical intersection involving the ground state is Jahn-Teller symmetry lowering from D 3h to C 2v , which is illustrated for the H 3 radical in Fig.…”

Section: Conical Intersectionsmentioning

confidence: 99%

“…26 The "spin-flip" (SF) variant of LR-TDDFT 327 has been suggested as a way to overcome this problem, as discussed in detail in Ref. 27. Briefly, SF-TDDFT uses a sacrificial reference state that is not the ground state of interest, but rather a state with higher spin multiplicity S + 1, for target states with total spin S. By combining single excitations with a single α → β spin flip, SF-TDDFT generates both ground and excited states of multiplicity 2S + 1 as spin-flipping excitations, meaning that both are obtained as solutions to a common eigenvalue problem.…”

Section: Conical Intersectionsmentioning

confidence: 99%

“…[20][21][22] LR-TDDFT is also becoming increasingly popular for photochemical applications, [23][24][25] despite some problems with the description of conical intersections. [26][27][28] In part, this popularity is due to a growing recognition that complete active-space (CAS-)SCF methods cannot be considered quantitative approaches for excited-state dynamics, [29][30][31][32] due to a lack of dynamical electron correlation effects. This chapter provides an overview of TDDFT and other DFT-based methods for computing excitation spectra, excited-state properties, and for simulating photochemical reactions, emphasizing theory rather than applications but with some molecular examples to motivate the discussion.…”

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confidence: 99%

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Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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This chapter provides a basic introduction to excited-state extensions of density functional theory (DFT), including time-dependent (TD-)DFT in both its linear-response and its explicitly time-dependent formulations. As applied to the Kohn-Sham DFT ground state, linear-response theory affords an eigenvaluetype problem for the excitation energies in a basis of singly-excited Slater determinants, and is widely known simply as "TDDFT" despite its frequency-domain formulation. This form of TDDFT is the mostly widely-used quantum-chemical method for excited states, due to a favorable combination of low cost and reasonable accuracy. The chapter surveys the accuracy of linear-response TDDFT, which is generally more sensitive to the details of the exchange-correlation functional as compared to ground-state DFT, and also describes some known systemic problems exhibited by this approach. Some of those problems can be corrected on a case-by-case basis using orbital-optimized, excited-state self-consistent field (SCF) calculations, in what is known as excited-state Kohn-Sham theory or a "∆SCF" procedure, a class of methods that includes restricted open-shell Kohn-Sham theory. Recent successes of these approaches are highlighted, including double excitations and core-level excitations. Finally, explicitly time-dependent (or "real-time") TDDFT involves propagation of the molecular orbitals in time following an external perturbation, according to the Kohn-Sham analogue of the time-dependent Schrödinger equation. The time-dependent approach has been used to model strong-field electron dynamics, and in the weak-field limit it provides a route to broadband spectra based on the time evolution of the dipole moment function. This is useful for describing high-energy excitations (as in x-ray spectroscopy) and in systems where the density of states is high, as demonstrated by a few examples.

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Section: Analytic Gradientsmentioning

confidence: 99%

Section: Conical Intersectionsmentioning

confidence: 99%

Section: Conical Intersectionsmentioning

confidence: 99%

Section: Conical Intersectionsmentioning

confidence: 99%

mentioning

confidence: 99%

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Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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Machine Learning Framework for Modeling Exciton Polaritons in Molecular Materials

Li,

Lubbers,

Tretiak

et al. 2024

J. Chem. Theory Comput.

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A light−matter hybrid quasiparticle, called a polariton, is formed when molecules are strongly coupled to an optical cavity. Recent experiments have shown that polariton chemistry can manipulate chemical reactions. Polariton chemistry is a collective phenomenon, and its effects increase with the number of molecules in a cavity. However, simulating an ensemble of molecules in the excited state coupled to a cavity mode is theoretically and computationally challenging. Recent advances in machine learning (ML) techniques have shown promising capabilities in modeling ground-state chemical systems. This work presents a general protocol to predict excited-state properties, such as energies, transition dipoles, and nonadiabatic coupling vectors with the hierarchically interacting particle neural network. ML predictions are then applied to compute the potential energy surfaces and electronic spectra of a prototype azomethane molecule in the collective coupling scenario. These computational tools provide a much-needed framework to model and understand many molecules' emerging excited-state polariton chemistry.

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XMECP: Reaching State-of-the-Art MECP Optimization in Multiscale Complex Systems

Xu,

Hao,

et al. 2024

J. Chem. Theory Comput.

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The Python-based program, XMECP, is developed for realizing robust, efficient, and state-of-the-art minimum energy crossing point (MECP) optimization in multiscale complex systems. This article introduces the basic capabilities of the XMECP program by theoretically investigating the MECP mechanism of several example systems including (1) the photosensitization mechanism of benzophenone, (2) photoinduced proton-coupled electron transfer in the cytosine−guanine base pair in DNA, (3) the spin-flip process in oxygen activation catalyzed by an iron-containing 2-oxoglutarate-dependent oxygenase (Fe/2OGX), and (4) the photochemical pathway of flavoprotein adjusted by the intensity of an external electric field. MECPs related to multistate reaction and multistate reactivity in large-scale complex biochemical systems can be well-treated by workflows suggested by the XMECP program. The branching plane updating the MECP optimization algorithm is strongly recommended as it provides derivative coupling vector (DCV) with explicit calculation and can equivalently evaluate contributions from non-QM residues to DCV, which can be nonadiabatic coupling or spin−orbit coupling in different cases. In the discussed QM/MM examples, we also found that the influence on the QM region by DCV can occur through noncovalent interactions and decay with distance. In the example of DNA base pairs, the nonadiabatic coupling occurs across the π−π stacking structure formed in the double-helix system. In contrast to general intuition, in the example of Fe/ 2OGX, the central ferrous and oxygen part contribute little to the spin−orbit coupling; however, a nearby arginine residue, which is treated by molecular mechanics in the QM/MM method, contributes significantly via two hydrogen bonds formed with αketoglutarate (α-KG). This indicates that the arginine residue plays a significant role in oxygen activation, driving the initial triplet state toward the productive quintet state, which is more than the previous knowledge that the arginine residue can bind α-KG at the reaction site by hydrogen bonds.

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Spin-Flip TDDFT for Photochemistry

Cited by 6 publications

References 119 publications

Density Functional Theory for Electronic Excited States

Density Functional Theory for Electronic Excited States

Machine Learning Framework for Modeling Exciton Polaritons in Molecular Materials

XMECP: Reaching State-of-the-Art MECP Optimization in Multiscale Complex Systems

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