Communication: Proper use of broken-symmetry calculations in antiferromagnetic polyradicals

Malrieu, Jean‐Paul; Trinquier, Georges

doi:10.1063/1.4953040

Cited by 13 publications

(9 citation statements)

References 22 publications

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“…(2) and (3). From a formal point of view, arguments both in favor [39,41] and against spin projection [42][43][44] have been presented. Studies in the literature [45,46] have revealed that the agreement with experiment is better for the unprojected formula as long as hybrid functionals are employed.…”

Section: Broken-symmetry Approach To Spin Couplingmentioning

confidence: 99%

Toward an automated analysis of exchange pathways in spin‐coupled systems

Steenbock

Herrmann

2017

J Comput Chem

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Understanding (super-)exchange coupling between local spins is an important task in theoretical chemistry and solid-state physics. We show that a Green's-function approach introduced earlier (Liechtenstein et al., J. Phys. F 1984, 14, L125; Steenbock et al., J. Chem. Theory Comput. 2015, 11, 5651) can be used for analyzing exchange coupling pathways in an automated fashion rather than by visual inspection of molecular orbitals. We demonstrate the capabilities of this approach by comparing it to previously published pathway analyses for hydroxy-bridged dinuclear copper complexes and an oxo-bridged dinuclear manganese complex, and employ it for discriminating between through-space and through-bond pathways in a naphthalene-bridged bisnickelocene complex. © 2017 Wiley Periodicals, Inc.

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Section: Broken-symmetry Approach To Spin Couplingmentioning

confidence: 99%

Toward an automated analysis of exchange pathways in spin‐coupled systems

Steenbock

Herrmann

2017

J Comput Chem

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“…Systematic comparisons between our predictions and the behavior of UDFT-B3LYP calculations will be presented for six series of compounds in section , confirming the validity of our model. Moreover the method enables one to predict whether the symmetry breaking may also concern deeper occupied MOs, for instance the HOMO-1 and the LUMO+1 orbitals, as has been observed in very long polyacenes and in regular fused rhomboidal polyacenes . Some comparative UHF results will be presented in section .…”

Section: Introductionmentioning

confidence: 98%

“…Moreover the method enables one to predict whether the symmetry breaking may also concern deeper occupied MOs, for instance the HOMO-1 and the LUMO+1 orbitals, as has been observed in very long polyacenes and in regular fused rhomboidal polyacenes. 54 Some comparative UHF results will be presented in section 3.3.…”

Section: Introductionmentioning

confidence: 99%

Can a Topological Approach Predict Spin-Symmetry Breaking in Conjugated Hydrocarbons?

Malrieu

Trinquier

2016

J. Phys. Chem. A

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The closed-shell mean-field single determinants of large alternant hydrocarbons are frequently unstable with respect to a possible spin-symmetry breaking which produces different orbitals for the α and β electrons, either in Hartree-Fock or in Kohn-Sham DFT calculations. The present work shows that one may easily predict whether such a symmetry breaking will take place from the elementary topological Hückel Hamiltonian which introduces a simple hopping integral t. The demonstration makes use of the simplest representation of the bielectronic repulsion, namely, the Hubbard bielectronic operator, reduced to an on-site repulsion U, and takes benefit of the mirror theorem. A recipe is proposed to determine the relevant t/U ratio for a given exchange-correlation potential. The symmetry-breaking phenomenon first concerns the mixing between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), but it may eventually run on other pairs of mirror orbitals. These symmetry breakings may take place while the other molecular orbitals keep a closed-shell character. The spin polarization of these MOs, appearing in typical unrestricted mean-field calculations, is an induced and amplifying effect, which has to be distinguished from the symmetry breaking itself. Special attention is paid to the possible appearance of multiple symmetry breakings, leading to a polyradical character. The model is tested on six series of polycyclic hydrocarbons. This elementary approach sheds new arguments on the debate concerning the di- or polyradical character of polyacenes.

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“…Broken-Symmetry DFT method (BS-DFT) [49][50][51][52] is an affordable method to describe open-shell singlets within a monodeterminantal scenario. This method, widely used for the treatment of diradical systems, 39,[53][54][55][56][57][58] introduces the breakdown of the spatial and spin symmetry in decoupled alpha and beta spin-orbital contributions. Then, the splitting of the spin contribution and the frontier orbital mixing introduces the correction of the static correlation.…”

Section: A Broken-symmetry Dftmentioning

confidence: 99%

Multi and Single-Reference Methods for the Analysis of Multi-State Peroxidation of Enolates

Ortega¹,

Gil‐Guerrero²,

Veselinova³

et al. 2021

Preprint

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In spite of being spin-forbidden, some enzymes are capable of catalyzing the incorporation of O2 (3Σ−g) to organic substrates without needing any cofactor. It has been established that the process followed by these enzymes starts with the deprotonation of the substrate forming an enolate. In a second stage, the peroxidation of the enolate formation occurs, a process in which the system changes its spin multiplicity from a triplet state to a singlet state. In this article, we study the addition of O2 to enolates using state-of-the-art multi-reference and single-reference methods. Our results confirm that intersystem crossing is promoted by stabilization of the singlet state along the reaction path. When multi-reference methods are used, large active spaces are required, and in this situation, Semistochastic Heat-Bath Configuration Interaction (SHCI) emerges as a powerful method to study these multi-configurational systems and is in good agreement with LCCSD(T) when the system is well-represented by a single-configuration.

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Communication: Proper use of broken-symmetry calculations in antiferromagnetic polyradicals

Abstract: Broken symmetry approach to density functional calculation of zero field splittings including anisotropic exchange interactions

Cited by 13 publications

References 22 publications

Toward an automated analysis of exchange pathways in spin‐coupled systems

Toward an automated analysis of exchange pathways in spin‐coupled systems

Can a Topological Approach Predict Spin-Symmetry Breaking in Conjugated Hydrocarbons?

Multi and Single-Reference Methods for the Analysis of Multi-State Peroxidation of Enolates

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