Effective exchange integrals for open-shell species by density functional methods

Yamanaka, Shusuke; Kawakami, Takashi; Nagao, Hidemi; Yamaguchi, Kizashi

doi:10.1016/0009-2614(94)01221-0

Cited by 311 publications

(217 citation statements)

References 27 publications

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“…The HF tends to underestimate D, and the pure and hybrid DFT tend to overestimate D, compared with the CASCI. This is the similar to the case of calculation of effective exchange integrals J [18].…”

Section: Discussionsupporting

confidence: 50%

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Ab initio calculation of the Dzyaloshinskii–Moriya parameters: Spin–orbit GSO‐HF, DFT, and CI approaches

Takeda

Yamanaka

Yamaguchi

2006

Int J of Quantum Chemistry

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ABSTRACT:We present ab initio methods to determine the Dzyaloshinskii-Moriya (DM) parameter, which provides the anisotropic effects of noncollinear spin systems. For this purpose, we explore various general spin orbital (GSO) approaches, such as Hartree-Fock (HF), density functional theory (DFT), and configuration interaction (CI), with one-electron spin-orbit coupling (SOC1). As examples, two simple D 3h -symmetric models, H 3 and B(CH 2 ) 3 , are examined. Implications of the computational results are discussed in relation to as isotropic and anisotropic interactions of molecular-based magnets.

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Section: Discussionsupporting

confidence: 50%

“…(13) or (15), the difference among HF, DFT, and CASCI are attributes to that of spin magnitudes. A noteworthy point is that this order on estimation of the DM parameter among the HF, DFT, CI solutions is similar to that of the J value [18].…”

Section: Computational Results and Discussion H 3 Model Moleculementioning

confidence: 70%

Ab initio calculation of the Dzyaloshinskii–Moriya parameters: Spin–orbit GSO‐HF, DFT, and CI approaches

Takeda

Yamanaka

Yamaguchi

2006

Int J of Quantum Chemistry

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“…This is easily performed using occupation numbers of natural orbitals that can be obtained by a standard ab initio package. The theoretical background is similar to approximated spin projection [68,69], but the formulation is based on spin-correlation functional [70,71]. In this method, we exploit the expectation value of Heisenberg model Hamiltonian given by,…”

Section: Appendix: Resonating Correctionmentioning

confidence: 99%

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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“…These methods yield encouraging results in various cases, [42][43][44] although it is easy to show that they are not size-consistent in general. From this perspective, while aiming for the same goal as these approximations, our methodology provides a more rigorous approach that is correct to the infinite order ofŜ 2 .…”

Section: Introductionmentioning

confidence: 99%

Bridging Single- and Multireference Domains for Electron Correlation: Spin-Extended Coupled Electron Pair Approximation

Tsuchimochi

Ten‐no

2017

J. Chem. Theory Comput.

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We propose a size-consistent generalization of the recently developed spin-extended configuration interaction with singles and doubles (ECISD), where a CI wave function is explicitly spin-projected. The size-consistent effect is effectively incorporated by treating quadruples within the formulation of coupled electron pair approximation. As in coupled-cluster theory, quadruple excitations are approximated by a disconnected product of double excitations. Despite its conceptual similarity to the standard single-and multireference analogues, such a generalization requires careful derivation, as the spin-projected CI space is non-orthogonal and overcomplete. Although our methods generally yield better results than ECISD, size-consistency is only approximately retained because the action of a symmetry-projection operator is size-inconsistent. In this work, we focus on simple models where exclusion-principle-violating terms, which eliminate undesired contributions to the correlation effects, are either completely neglected or averaged. These models possess an orbital-invariant energy functional that is to be minimized by diagonalizing an energy-shifted effective Hamiltonian within the singles and doubles manifold. This allows for a straightforward generalization of the ECISD analytical gradients needed to determine molecular properties and geometric optimization. Given the multireference nature of the spin-projected Hartree-Fock method, the proposed approaches are expected to handle static correlation, unlike single-reference analogues. We critically assess the performance of our methods using dissociation curves of molecules, singlet-triplet splitting gaps, hyperfine coupling constants, and the chromium dimer. The size-consistency and size-extensivity of the methods are also discussed.

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Effective exchange integrals for open-shell species by density functional methods

Cited by 311 publications

References 27 publications

Ab initio calculation of the Dzyaloshinskii–Moriya parameters: Spin–orbit GSO‐HF, DFT, and CI approaches

Ab initio calculation of the Dzyaloshinskii–Moriya parameters: Spin–orbit GSO‐HF, DFT, and CI approaches

Density functional study of manganese dimer

Bridging Single- and Multireference Domains for Electron Correlation: Spin-Extended Coupled Electron Pair Approximation

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