Accuracy of density functional theory methods for the calculation of magnetic exchange couplings in binuclear iron(III) complexes

Joshi, Ritesh; Phillips, Jordan J.; Mitchell, Kylie J.; Christou, George; Jackson, Koblar Alan; Peralta, Juan E.

doi:10.1016/j.poly.2019.114194

Cited by 22 publications

(42 citation statements)

References 72 publications

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“…for the benchmark set [36][37][38]. This study extends previous SF-TDDFT benchmarking work on binuclear Cu(II) systems [28] to more challenging Fe(III) binuclear systems with a much larger number of unpaired electrons.…”

Section: Investigate the Functional And Basis-set Dependence Of Excha...supporting

confidence: 60%

“…Exchange couplings for complexes 1, 2, 4, 7, 8 and 12 of Fig. 3 are also available from BS-DFT calculations [38]. One of the best performing functional of this BS-DFT work is the hybrid range-separated HSE functional (also known as HSE06), which gives MAE of 5.4 cm −1 , to be compared with MAE of 3.8 cm −1 obtained with our NC-SFTDDFT/ωPBEh protocol.…”

Section: B Benchmark Calculationsmentioning

confidence: 99%

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Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

Kotaru

Kähler

Alessio

et al. 2022

Preprint

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Low-energy spectra of single-molecule magnets (SMMs) are often described by Heisenberg Hamiltonians. Within this formalism, exchange interactions between magnetic centers determine the ground-state multiplicity and energy separation between the ground and excited states. In this contribution, we extract exchange coupling constants (J) for a set of iron (III) binuclear and tetranuclear complexes from all-electron calculations using non-collinear spin-flip time-dependent density functional theory (NC-SF-TDDFT). For 12 binuclear complexes with J-values ranging from -6 to -132 cm−1, our benchmark calculations using the short-range hybrid ωPBEh functional and 6-31G(d,p) basis set agree well with the experimentally derived values (mean absolute error of 4.7 cm−1). For the tetranuclear SMMs, the computed J constants are within 6 cm−1 from the experimentally derived values. We explore the range of applicability of the Heisenberg model by analyzing bonding patterns in these Fe(III) complexes using natural orbitals (NO), their occupations, and the number of effectively unpaired electrons. The results illustrate the efficiency of the spin-flip protocol for computing the exchange couplings and the utility of the NO analysis in assessing the validity of effective spin Hamiltonians.

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Section: Investigate the Functional And Basis-set Dependence Of Excha...supporting

confidence: 60%

Section: B Benchmark Calculationsmentioning

confidence: 99%

Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

Kotaru

Kähler

Alessio

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…However, many examples show that the optimal functional is not transferable from system to system. For example, it was observed that B3LYP [47,48] can give satisfactory results for copper [54][55][56][57] and cobalt [58,59] complexes, but is not the best functional for chromium [60], manganese [61] and iron [62] dimers. In these latter cases, TPSS0 [63,64], TPSSh [65] and M06 [66], respectively, are the best performing functionals to describe the experimental results.…”

Section: B Broken-symmetry Density Functional Theorymentioning

confidence: 99%

Magnetic exchange coupling in Cu dimers studied with modern multireference methods and broken-symmetry coupled cluster theory

et al. 2021

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Spin-state energetics of exchange-coupled copper complexes pose a persistent challenge for applied quantum chemistry. Here, we provide a comprehensive comparison of all available theoretical approaches to the problem of exchange coupling in two antiferromagnetically coupled bis-μ-hydroxo Cu(II) dimers. The evaluated methods include multireference methods based on the density matrix renormalization group (DMRG), multireference methods that incorporate dynamic electron correlation either perturbatively, such as the N-electron valence state perturbation theory, or variationally, such as the difference-dedicated configuration interaction. In addition, we contrast the multireference results with those obtained using broken-symmetry approaches that utilize either density functional theory or, as demonstrated here for the first time in such systems, a local implementation of coupled cluster theory. The results show that the spin-state energetics of these copper dimers are dominated by dynamic electron correlation and represent an impossible challenge for multireference methods that rely on brute-force expansion of the active space to recover correlation energy. Therefore, DMRG-based methods even at the limit of their applicability cannot describe quantitatively the antiferromagnetic exchange coupling in these dimers, in contrast to dinuclear complexes of earlier transition metal ions. The convergence of the broken-symmetry coupled cluster approach is studied and shown to be a limiting factor for the practical application of the method. The advantages and disadvantages of all approaches are discussed, and recommendations are made for future developments.

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“…3. Several of these complexes have been studied using broken symmetry DFT (BS-DFT) approach by Joshi et al [35]. All these complexes have Fe (III) atoms with d 5 configuration.…”

Section: Computational Detailsmentioning

confidence: 99%

“…We begin by assessing the applicability of the HDvV treatment in the binuclear complexes by employing density-based analysis and natural orbitals (NOs) [28,32]. We then investigate the functional and basis-set dependence on exchange coupling constants in binu-clear complexes [33][34][35]. For tetranuclear SMMs, we simplify the problem of parameterizing the Heisenberg Hamiltonian for a multi-center molecular magnet by performing only a single SF calculation from the highest-multiplicity state, following the approach of Mayhall and Head-Gordon [36].…”

mentioning

confidence: 99%

Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

Kotaru

Alessio

Krylov

2021

Preprint

View full text Add to dashboard Cite

Low-energy spectra of single-molecule magnets (SMMs) are often described by the Heisenberg Hamiltonian. Within this formalism, exchange interactions between magnetic centers determine the ground-state multiplicity and energy separation between the ground and excited states. In this contribution, we extract exchange coupling constants (J) for a set of iron (III) binuclear and tetranuclear complexes from all-electron calculations using non-collinear spin-flip time-dependent density functional theory (NC-SF-TDDFT). For the series of binuclear complexes with J-values ranging from -6 to -132 cm−1 , our benchmark calculations using the short-range hybrid LRC-ωPBEh functional and 6-31G(d,p) basis set agree well (mean absolute error of 4.7 cm−1) with the experimentally derived values. For the tetranuclear SMMs, the computed J constants are within 6 cm−1 from the values extracted from the experiment. We explore the range of applicability of the Heisenberg model by analyzing the radical character in the binuclear iron (III) complexes using natural orbitals (NO) and their occupations. On the basis of the number of effectively unpaired electrons and the NO occupancies, we attribute larger errors observed in strongly anti-ferromagnetic species to an increased ionic character. The results illustrate the efficiency of the spin-flip protocol for computing the exchange couplings and the utility of the NO analysis in assessing the validity of effective spin Hamiltonians.

show abstract

Accuracy of density functional theory methods for the calculation of magnetic exchange couplings in binuclear iron(III) complexes

Cited by 22 publications

References 72 publications

Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

Magnetic exchange coupling in Cu dimers studied with modern multireference methods and broken-symmetry coupled cluster theory

Magnetic Exchange Interactions in Binuclear and Tetranuclear Iron (III) Complexes Described by Spin-Flip DFT and Heisenberg Effective Hamiltonians

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