Ab initio molecular orbital calculations of effective exchange integrals between transition metal ions

Yamaguchi, Kizashi; Tsunekawa, Tetsuya; Toyoda, Yasuyuki; Fueno, Takayuki

doi:10.1016/0009-2614(88)87049-0

Cited by 156 publications

(114 citation statements)

References 17 publications

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“…As the computational result using KS-DFT/hybrid-DFT are mainly determined by the exchange correlation term we employed, the issue is what type of exchange correlation functional is efficient to reproduce the local magnetic interaction and chemical bonding of manganese dimer. For the purpose, it is important to remember that the spinprojected unrestricted Hartree-Fock (HF) by Nesbet [25] and Yamaguchi et al [35] yields results that are compatible with experimental and MRMP2 results. In particular, magnetic interaction (J) value reported by Yamaguchi et al is Ϫ7 cm Ϫ1 [35], which is similar to experimental one (Ϫ9 cm Ϫ1 ) [37], implying the exact HF exchange is essential for J of this troublesome species.…”

Section: Introductionmentioning

confidence: 76%

“…For the purpose, it is important to remember that the spinprojected unrestricted Hartree-Fock (HF) by Nesbet [25] and Yamaguchi et al [35] yields results that are compatible with experimental and MRMP2 results. In particular, magnetic interaction (J) value reported by Yamaguchi et al is Ϫ7 cm Ϫ1 [35], which is similar to experimental one (Ϫ9 cm Ϫ1 ) [37], implying the exact HF exchange is essential for J of this troublesome species. Thus, in this study, we will examine whether the results similar to MRMP and experimental ones can be obtained within the KS-DFT/hybrid DFT or HF plus DFT correlation methods.…”

Section: Introductionmentioning

confidence: 76%

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Density functional study of manganese dimer

Yamanaka

Ukai

Nakata

et al. 2007

Int J of Quantum Chemistry

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ABSTRACT:Chemical bonding and magnetic interaction of manganese dimer (Mn 2 ) are still in controversy in experimental and theoretical studies. In this work, we examined various exchange correlation functionals of Kohn-Sham density functional theory (DFT), together with hybrid-DFT, and Hartree-Fock plus DFT approaches on description of Mn 2 . We found that, in contrast to pure DFT functionals, the experimentally reported features of chemical bonding and antiferromagnetic interactions of Mn 2 can be reproduced by employing the Hartree-Fock exchange terms. Thus, it is recommended to employ HF plus DFT, or hybrid DFT with large HF portion approach for the case that the direct interactions among manganese atoms play a major role to determine the electronic structure, such as manganese clusters.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 76%

Density functional study of manganese dimer

Yamanaka

Ukai

Nakata

et al. 2007

Int J of Quantum Chemistry

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“…4, though these MOs are actually symmetry-broken because of the strong electron correlation as described by the dierent-orbitals-for-dierent-spins as shown by 7 in Fig. 4 [31].…”

Section: Superexchange Interactionsmentioning

confidence: 96%

“…The A illustrates a helical spin structure for three spin systems. B and C depict spin structures with the cone-and top-type symmetries, respectively stabilization of the low-spin state by this interaction is often called the superexchange mechanism [31]. The heroatoms in 1 can be used as antiferromagnetic couplers in organic magnetic olygomers and polymers.…”

Section: Superexchange Interactionsmentioning

confidence: 99%

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Symmetry and broken symmetries in molecular orbital descriptions of unstable molecules II. Alignment, flustration and tunneling of spins in mesoscopic molecular magnets

Yamaguchi

Yamanaka

Nishino

et al. 1999

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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As an extention of previous work [Yamaguchi K (1983) J Mol Structure (Theochem) 103:101], our theoretical eorts toward molecular materials are brie¯y reviewed. Axial, helical and general (cone, tetrahedron, etc) spin structures of carbon clusters, manganese oxide clusters and iron-sulfur clusters were investigated using the classical Heisenberg model and generalized HartreeFock theory. The spin¯ustrations in the clusters were also studied in relation to theoretical descriptions of the magnetism and the chemical bonds in active sites of several enzymes. The macroscopic quantum tunneling and coherence of spins in the manganese oxide clusters were analyzed using the instanton model, and the tunneling rate of spins was calculated by the coherent state path integral method. The spin transitions induced by an external magnetic ®eld were studied by the path integral Monte Carlo method. The theoretical results were explained in terms of the symmetry and broken symmetry of the wavefunctions in the mesoscopic molecular systems, which are intermediate in the scale factor. The results were also applied to molecular design of mesoscopic clusters of clusters in the intermediate and strong correlation regime. The active control of spins is ®nally discussed from the viewpoint of functionalities in molecular and biological materials, and technological applications of mesoscopic molecular magnets are discussed with regard to quantum computing.

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The Symmetry-Broken Formalism Applied to the Electronic Structure of an Iminosemiquinone Copper(II) Catalyst: A Key to the Qualitative Understanding of Its Reactivity

2001

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A concise outline of the known derivation of the singlet-triplet energy-gap equations within the symmetry-broken wavefunction framework is given. They allow a computation of the singlet-triplet energy gap for molecules that exhibit a weak antiferromagnetic coupling of electrons. The accuracy of the equations is assessed by computation of the singlet-triplet gaps in model Na2 molecules. Various antiferromagnetic coupling strengths are simulated by the use of different Na-Na bond lengths in the computations. The singlet-triplet energy gaps obtained with the different equations are compared with the gaps computed with the more accurate coupled-cluster methods. Subsequently, the equations are applied to an iminosemiquinone copper(II) complex found previously to have remarkable catalytic properties. The application is performed by employing wave-function equations but with quantities computed within the density functional framework. The electronic ground state of this complex is computed to be a singlet state, which is also the experimental finding. Moreover, the experimental geometry and the singlet-triplet gap are reasonably reproduced by the computation. A straightforward method to determine the magnetic orbitals is suggested and applied. We illustrate that the form of the magnetic orbitals indicates in a qualitative manner that hydrogen-atom abstraction should be a major reaction pathway of the iminosemiquinone copper(II) complex. Hydrogen-atom abstraction has been suggested previously to be the rate-determining step in a catalytic process initiated by the iminosemiquinone copper(II) complex. The results support the notion that the form of the magnetic orbitals might be a qualitative indicator for the reactivity of molecules that exhibit weak antiferromagnetic coupling.

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Ab initio molecular orbital calculations of effective exchange integrals between transition metal ions

Cited by 156 publications

References 17 publications

Density functional study of manganese dimer

Density functional study of manganese dimer

Symmetry and broken symmetries in molecular orbital descriptions of unstable molecules II. Alignment, flustration and tunneling of spins in mesoscopic molecular magnets

The Symmetry-Broken Formalism Applied to the Electronic Structure of an Iminosemiquinone Copper(II) Catalyst: A Key to the Qualitative Understanding of Its Reactivity

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