An iterative difference-dedicated configuration interaction. Proposal and test studies

García, Víctor Manuel Pérez; Castell, O.; Caballol, Rosa; Malrieu, Jean‐Paul

doi:10.1016/0009-2614(95)00438-a

Cited by 129 publications

(71 citation statements)

References 23 publications

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“…In order to overcome the possible dependence of our results on the starting molecular orbital set, we have obtained the S -T average natural orbitals by means of an iterative procedure, proposed by Garcia et al 35 and implemented in the DDCI scheme. An average density matrix for the singlet and triplet states is built: R ϭ(R S ϩR T )/2.…”

Section: A Dependence Of the J Value On The Molecular Orbital Choicementioning

confidence: 99%

Accurate ab initio determination of magnetic interactions and hopping integrals in La2−xSrxCuO4 systems

Calzado

Sanz

Malrieu

2000

The Journal of Chemical Physics

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Articles you may be interested inThe nature of magnetic interactions and electron transfer processes in La 2Ϫx Sr x CuO 4 systems are studied, by means of an ab initio embedded cluster model approach, using a difference dedicated configuration interaction ͑DDCI͒ procedure. For the undoped system, the crucial role played by the ligand to metal charge transfer ͑LMCT͒ configurations in the magnetic process makes necessary the use of an enlarged DDCI space, which explicitly takes account of the relaxation of these LMCT configurations. This procedure allows us to approach the experimental magnetic coupling constant value. In hole-doped systems, the value obtained for the electron transfer integral, t, is of 0.54-0.57 eV. The extra hole, characterized from the nature and occupation of differential natural orbitals, has a strong p character ͑approximately 50%͒ and is essentially localized in CuO 2 planes. These results are in agreement with the experimental evidence about these kinds of compounds. Neither the value of t nor the nature of the extra hole are seriously affected by the optimization of the orbitals used in the CI expansion. This suggests that a t -J effective Hamiltonian is an adequate model to study the electronic properties of these systems.

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Section: A Dependence Of the J Value On The Molecular Orbital Choicementioning

confidence: 99%

Accurate ab initio determination of magnetic interactions and hopping integrals in La2−xSrxCuO4 systems

Calzado

Sanz

Malrieu

2000

The Journal of Chemical Physics

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“…The resulting MOs are employed in subsequent DDCI calculations until convergence (iterative DDCI or IDDCI calculations). 90 This procedure has been shown to be efficient in eliminating any dependence of the DDCI results on the starting MOs, taking into account the orbital relaxation induced by the electron correlation. The shape of the so-obtained MOs is represented in Figure 5, the most relevant feature being the enhancement of the electron density on the central NO groups, which is in line with the increase of the calculated J bond value at DDCI(2/2) level (Table 2) Unfortunately, there are no experimental data available with respect to the spin density in compound 1 or any other of the compounds investigated in the present work, which could validate the shape of the optimized magnetic MOs.…”

Section: Resultsmentioning

confidence: 99%

Analysis of the Magnetic Exchange Interactions in Yttrium(III) Complexes Containing Nitronyl Nitroxide Radicals

et al. 2017

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“…The introduction of dynamical correlation via NEVPT2 recovered some of the important contributions given by the bridging ligand orbitals to the super-exchange mechanism and both the experimental sign and an acceptable magnitude of 5.32 cm −1 for J 12 have been then reached. Possible strategies to further improve this result would require the introduction of a dedicated CI procedure [33] or equivalent [34] on top of the CASSCF instead of NEVPT2. Another possible source of the discrepancy can reside in the limited flexibility of the wavefunction resulting by a CAS(5,5), i.e., the so called 3d double-shell effect [35] or the missing of the explicit inclusion of bridging ligands orbitals in the CAS [35].…”

Section: X-ray Structurementioning

confidence: 99%

The Role of Anisotropic Exchange in Single Molecule Magnets: A CASSCF/NEVPT2 Study of the Fe4 SMM Building Block [Fe2(OCH3)2(dbm)4] Dimer

Lunghi

Totti

2016

Inorganics

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Abstract:The rationalisation of single molecule magnets' (SMMs) magnetic properties by quantum mechanical approaches represents a major task in the field of the Molecular Magnetism. The fundamental interpretative key of molecular magnetism is the phenomenological Spin Hamiltonian and the understanding of the role of its different terms by electronic structure calculations is expected to steer the rational design of new and more performing SMMs. This paper deals with the ab initio calculation of isotropic and anisotropic exchange contributions in the Fe(III) dimer [Fe 2 (OCH 3 ) 2 (dbm) 4 ]. This system represents the building block of one of the most studied Single Molecule Magnets ([Fe 4 RC(CH 2 O) 3 ) 2 (dpm) 6 ] where R can be an aliphatic chain or a phenyl group just to name the most common functionalization groups) and its relatively reduced size allows the use of a high computational level of theory. Calculations were performed using CASSCF and NEVPT2 approaches on the X-ray geometry as assessment of the computational protocol, which has then be used to evinced the importance of the outer coordination shell nature through organic ligand modelization. Magneto-structural correlations as function of internal degrees of freedom for isotropic and anisotropic exchange contributions are also presented, outlining, for the first time, the extremely rapidly changing nature of the anisotropic exchange coupling.

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An iterative difference-dedicated configuration interaction. Proposal and test studies

Cited by 129 publications

References 23 publications

Accurate ab initio determination of magnetic interactions and hopping integrals in La2−xSrxCuO4 systems

Accurate ab initio determination of magnetic interactions and hopping integrals in La2−xSrxCuO4 systems

Analysis of the Magnetic Exchange Interactions in Yttrium(III) Complexes Containing Nitronyl Nitroxide Radicals

The Role of Anisotropic Exchange in Single Molecule Magnets: A CASSCF/NEVPT2 Study of the Fe4 SMM Building Block [Fe2(OCH3)2(dbm)4] Dimer

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