Comparison between spin restricted and unrestricted post-Hartree—Fock calculations of effective exchange integrals in Ising and Heisenberg models

Yamaguchi, Kizashi; Okumura, Mitsutaka; Mori, Wasuke; Maki, Jun; Takada, Kei; Noro, Takeshi; Tanaka, Kiyoshi

doi:10.1016/0009-2614(93)89124-z

Cited by 85 publications

(63 citation statements)

References 25 publications

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“…Supplementary Materials: The following are available online at www.mdpi.com/2073-4352/7/7/222/s1, Figure S1: V S (r), E S (r) and the favored H 2 O adsorption structure for Rh 13 at the decatet spin-state; Table S1: spin multiplicity and <S 2 > expectation values for the Pt 4 and TM 8 nanoclusters; Table S2: spin multiplicity and <S 2 > expectation values for the TM 13 nanoclusters; Table S3: spin projection corrected and non-corrected H 2 O interaction energies for Ir 13 and Rh 13 ; Table S4: site-resolved H 2 O adsorption data, V S,max , and E S,min for all TM 13 nanoclusters; Table S5: the number of V S,max , and E S,min as well as the s-, d-and p-occupation for Rh 13 at the decatet spin-state; Table S6: site-resolved H 2 O adsorption data, V S,max , and E S,min for Rh 13 at the decatet spin-state; additional computational data for Figures 1 and 3; optimized coordinates; supplementary references [60][61][62][63][64][65][66][67][68][69][70][71][72].…”

Section: Discussionmentioning

confidence: 99%

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

2017

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Understanding the molecular interaction behavior of transition metal nanoclusters lies at the heart of their efficient use in, e.g., heterogeneous catalysis, medical therapy and solar energy harvesting. For this purpose, we have evaluated the applicability of the surface electrostatic potential [V S (r)] and the local surface electron attachment energy [E S (r)] properties for characterizing the local Lewis acidity of a series of low-energy TM 13 transition metal nanoclusters (TM = Au, Cu, Ru, Rh, Pd, Ir, Pt, Co), including also Pt 7 Cu 6 . The clusters have been studied using hybrid Kohn-Sham density functional theory (DFT) calculations. The V S (r) and E S (r), evaluated at 0.001 a.u. isodensity contours, are used to analyze the interactions with H 2 O. We find that the maxima of V S (r), σ-holes, are either localized or diffuse. This is rationalized in terms of the nanocluster geometry and occupation of the clusters's, p and d valence orbitals. Our findings motivate a new scheme for characterizing σ-holes as σ s (diffuse), σ p (localized) or σ d (localized) depending on their electronic origin. The positions of the maxima in V S (r) (and minima in E S (r)) are found to coincide with O-down adsorption sites of H 2 O, whereas minima in V S (r) leads to H-down adsorption. Linear relationships between V S,max (and E S,min ) and H 2 O interaction energies are further discussed.

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Section: Discussionmentioning

confidence: 99%

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

2017

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“…(12) are quite similar, showing that the orbital overlaps between the magnetic orbitals are small. However, the t (APUHF) values are dierent from the corresponding t values by UNO CASSCF, which utilizes two active orbitals and two active electrons f2Y 2g [23,29]. On the other hand, the AP-DFT method approximately reproduces the CA-SSCF results.…”

Section: Linear Clusters Of 13-biradicalsmentioning

confidence: 88%

“…The LoÈ wdin-type spinprojection scheme [38] is utilized for this purpose; however, it often provides wrong t values because of the approximations introduced [38]. Alternately, approximate spin projections [3,29,30] are feasible for G(U)HF-based and spin-polarized DFT methods to calculate potential curves for dissociations from near closed-shell to the localized limit. To this end, we have considered an approximate but size-consistent spinprojection procedure, where the denominator in Eq.…”

Section: Size-consistent Spin Projectionmentioning

confidence: 98%

“…The spin-projection eect is remarkable for DFT, indicating that the orbital overlap between magnetic orbitals is relatively large because of the superexchange mechanism. This in turn indicates that UHF underestimates the superexchange interaction, and therefore should be improved by the MP and CC corrections [29]. Next, we examined the trimer (8) as illustrated in Fig.…”

Section: Linear Clusters Of 13-biradicalsmentioning

confidence: 99%

“…(5) means Mùller-Plesset (MP) perturbation and CC methods as post GHF(UHF) approximations to include dynamical correlation eects [29]. Since the GHF solution often reduces to UHF(ASDW) in the LS state for the case of 1D spin structure, the t value can be calculated within the UHF approximation as illustrated in Fig.…”

Section: Spin Structure and Heisenberg Modelmentioning

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

Self Cite

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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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A Benzene‐1,3,5‐Triaminyl Radical Fused with Zn^II‐Porphyrins: Remarkable Stability and a High‐Spin Quartet Ground State

Shimizu

Osuka

2018

Angewandte Chemie

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A benzene‐1,3,5‐triaminyl radical fused with three ZnII‐porphyrins was synthesized through a three‐fold oxidative fusion reaction of 1,3,5‐tris(ZnII‐porphyrinylamino)benzene followed by oxidation with PbO2 as key steps. This triaminyl radical has been shown to possess a quartet ground state with a doublet–quartet energy gap of 3.1 kJ mol−1 by superconducting quantum interference device (SQUID) studies. Despite its high‐spin nature, this triradical is remarkably stable, which allows its separation and recrystallization under ambient conditions. Moreover, this triradical can be stored as a solid for more than one year without serious deterioration. The high stability of the triradical is attributed to effective spin delocalization over the porphyrin segments and steric protection at the nitrogen centers and the porphyrin meso positions.

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Comparison between spin restricted and unrestricted post-Hartree—Fock calculations of effective exchange integrals in Ising and Heisenberg models

Cited by 85 publications

References 25 publications

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

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

A Benzene‐1,3,5‐Triaminyl Radical Fused with Zn^II‐Porphyrins: Remarkable Stability and a High‐Spin Quartet Ground State

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Comparison between spin restricted and unrestricted post-Hartree—Fock calculations of effective exchange integrals in Ising and Heisenberg models

Cited by 85 publications

References 25 publications

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

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

A Benzene‐1,3,5‐Triaminyl Radical Fused with ZnII‐Porphyrins: Remarkable Stability and a High‐Spin Quartet Ground State

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Product

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A Benzene‐1,3,5‐Triaminyl Radical Fused with Zn^II‐Porphyrins: Remarkable Stability and a High‐Spin Quartet Ground State