Modified virtual orbitals for CI calculations of energy splitting in organic diradicals

Barone, Vincenzo; Cacelli, Ivo; Ferretti, Alessandro; Prampolini, Giacomo

doi:10.1039/b902051a

Cited by 16 publications

(53 citation statements)

References 43 publications

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“…With this last paper, which follows our previous studies where we first investigated on the effects and simplifications of molecular fragmentation, 14,15 and the advantages of using MVOs in place of canonical orbitals, 18 we think we have at hand a very promising computational tool for the calculation of J. We are confident in the success of its application to larger diradical species of wide interest for technological applications in magnetic-based devices.…”

Section: Discussionmentioning

confidence: 70%

“…8 has shown to be the most accurate and appropriate for the interpretation of the various contributions to J. 18 We want now to report on the application of perturbation theory as a further and ultimate tool for reducing substantially the computational effort. A reasonable approximation is obtained by considering a much reduced configurational space, such as that of the so called DDCI2 model, 11 which has been found to give, for organic diradicals, values of J with acceptable accuracy.…”

Section: Accurate Yet Feasible Post-hartree-fock Computation Of Magnementioning

confidence: 99%

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Accurate yet feasible post-Hartree–Fock computation of magnetic interactions in large biradicals through a combined variational/perturbative approach: Setup and validation

Barone

Cacelli

Ferretti

et al. 2009

The Journal of Chemical Physics

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We present a scheme for the calculation of the spin-spin coupling term J in diradicals which is quantitatively accurate and computationally cheap. The method exploits the use of modified virtual orbitals and perturbation theory, incorporated in a multireference configuration interaction approach. The results obtained for model diradical species which exhibit ferromagnetic and antiferromagnetic coupling are fully satisfactory and very promising for future applications of the method to larger molecular systems of technological interest in magnetic-based devices.

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Section: Discussionmentioning

confidence: 70%

Section: Accurate Yet Feasible Post-hartree-fock Computation Of Magnementioning

confidence: 99%

Accurate yet feasible post-Hartree–Fock computation of magnetic interactions in large biradicals through a combined variational/perturbative approach: Setup and validation

Barone

Cacelli

Ferretti

et al. 2009

The Journal of Chemical Physics

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“…Thereafter, a restricted Open-shell Hartree-Fock-SCF (ROHF-SCF) calculation was carried out using the Gamess program, 43 on the same spin state and geometry and with the same basis set of the previous DFT calculation. The resulting 1162 canonical molecular orbitals (MOs) were then modified using the QUIOLA program, 40 with the aim of enforcing fragment localization and concentrating the charge of the lowest virtual MOs near the spin centers 44,45 (see also Supporting Information). As mentioned above, the magnetic orbitals have negligible contributions from the pendant phenyls, so that the MOs localized on these moieties (for a total of 574 MOs) are expected to play a negligible role in tuning the energy splittings.…”

Section: Computational Route To Magnetic Splittingsmentioning

confidence: 99%

Quantitative prediction and interpretation of spin energy gaps in polyradicals: the virtual magnetic balance

Barone

Cacelli

Ferretti

et al. 2017

Phys. Chem. Chem. Phys.

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Open-shell organic molecules possessing more than two unpaired electrons and sufficient stability even at room temperature are very unusual, but few were recently synthesized that promise a number of fascinating applications. Unfortunately, reliable structural information is not available and only lower limits can be estimated for energy splittings between the different spin states. On these grounds, we introduce here an effective 'virtual magnetic balance', a robust and user-friendly tool purposely tailored for polyradicals and devised to be used in parallel with experimental studies. The main objective of this tool is to provide reliable structures and quantitative splittings of spin states of large, complex molecules. We achieved this objective with reasonable computation times and in a theoretical framework that allows disentanglement of different stereo-electronic effects contributing to the overall experimental result. A recently synthesized tetraradical with remarkable chemical stability was used as a case study.

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“…DDCI is frequently considered as the best available method for the calculation of magnetic couplings [7][8][9][10][11]25]. …”

Section: Iib Methodological Aspects and Accurate Extraction Of The Lmentioning

confidence: 99%

Physical analysis of the through-ligand long-distance magnetic coupling: spin-polarization versus Anderson mechanism

Térencio

Bastardis

Suaud

et al. 2011

Phys. Chem. Chem. Phys.

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Physical analysis of the through-ligand long-distance magnetic coupling: spin-polarization versus Anderson mechanismAuthors: T. Terencio (a) , R. Bastardis (b) , N. Suaud (a) , D. Maynau (a) , J. Bonvoisin (c) , J.P.Malrieu (a) , C. J. Calzado (d) and N. Guihéry (a) Affiliations:(a AbstractThe physical factors governing the magnetic coupling between two magnetic sites are analyzed and quantified as functions of the length of the bridging conjugated ligand. Using wave-function-theory based ab initio calculations, it has been possible to separate and calculate the various contributions to the magnetic coupling, i.e. the direct exchange, the spin polarization and the kinetic exchange. It is shown on model systems that while the Anderson mechanism brings the leading contribution for short-length ligands, the spin polarization dominates the through-long-ligand couplings. Since the spin polarization decreases more slowly than the kinetic exchange, highly spin polarizable bridging ligand would generate a good magneto-communication between interacting magnetic units. 2 I IntroductionThe electronic communication between two magnetic sites connected through bridges has been a topic of large interest in molecular electronics [1][2][3][4] and spintronics [5,6]. Much effort from experimentalists has been invested in the elucidation of the role of extended bridges between two interacting units, both concerning the electron transfer in mixed valence compounds (electro-communication) and the magnetic coupling of unpaired electrons in pure magnetic compounds (magneto-communication).From a theoretical point of view, several works reviewed in references [7,8] Furthermore, the separation of both mechanisms enables us to quantify all effective interactions involved in the magnetic coupling, i.e. direct exchange, spin polarization, hopping integral t and on-site electron repulsion U.In section II, the various physical factors governing the magnetic interaction are briefly summarized and the methodology required to accurately reproduce them is recalled. Section III is devoted to an ab initio study of the different contributions to the magnetic coupling as

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Modified virtual orbitals for CI calculations of energy splitting in organic diradicals

Cited by 16 publications

References 43 publications

Accurate yet feasible post-Hartree–Fock computation of magnetic interactions in large biradicals through a combined variational/perturbative approach: Setup and validation

Accurate yet feasible post-Hartree–Fock computation of magnetic interactions in large biradicals through a combined variational/perturbative approach: Setup and validation

Quantitative prediction and interpretation of spin energy gaps in polyradicals: the virtual magnetic balance

Physical analysis of the through-ligand long-distance magnetic coupling: spin-polarization versus Anderson mechanism

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