Structural dependence of the singlet-triplet gap in doubly bridged copper dimers: a variational CI calculation

Castell, O.; Miralles, Josefa; Caballol, Rosa

doi:10.1016/0301-0104(94)87014-4

Cited by 61 publications

(49 citation statements)

References 25 publications

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“…Many proposals have been made for directly evaluating energy differences, such as the equation of motion (EOM) method [42], in particular combined with coupled-cluster methods (EOMCC) [43], or the specific CIs of Goddard and coworkers [44,45]. The DDCI [9][10][11] method also consists of a specific CI treatment adapted to the energy difference being searched and is based on a zero-order description of the transition in terms of n electrons in m active orbitals (in most cases, two electrons in two active orbitals) Downloaded by ["Queen's University Libraries, Kingston"] at 23:57 20 September 2013 defining the CAS as the zero-order model space. The configurations contributing to the transition at the second order of the expansion of the effective Hamiltonian built in the model space are included in the CI space which is then processed variationally.…”

Section: Selection Of the CI Space For The Evaluation Of Transition Ementioning

confidence: 99%

“…Theoretically, they have been used also as a severe test for new methods and, in the same sense, for calibrating basis sets and the percentage of inclusion of electron correlation by comparison with full configuration interaction (FCI) results when available [6][7][8]. In this study, we report the results obtained for these compounds using the differencededicated configuration interaction (DDCI) method, which has been shown [9][10][11] to evaluate energy gaps very efficiently.…”

Section: Introductionmentioning

confidence: 97%

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Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

et al. 1996

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Ab initio calculations including correlation energy are reported on a series of halogen-substituted carbenes and silylenes: CH 2, CHF, CF 2, CHC1, CC12, CHBr, CBr2, Sill2, SiHF, SiF2, using the difference-dedicated configuration interaction method. All these compounds with the exception of CH 2 have singlet ground states. The singlet-triplet energy differences are in very good agreement with experiment when available, as well as with other high level calculations. The singlet-triplet separation is also determined in trifluoromethyl carbenes, CHCF3, CFCF3, CCICF 3 and CBrCF 3. The CF 3 substituent has little influence on the energy gap since CHCF 3 like CH 2 has a triplet ground state, with a gap of 11"1 kcal mo1-1, and CFCF~, CCICF 3 and CBrCF 3 have singlet ground states, like CHF, CHCI and CHBr, with gaps of -17.6, -5"4, and -3"5 kcal mo1-1.

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Section: Selection Of the CI Space For The Evaluation Of Transition Ementioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

et al. 1996

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“…The redundant information may be used to check that the different roots of the CASCI matrix obtained from the Davidson procedure are in fact those which one wants to compute effectively. [46][47][48] Since the application of the DDCI approach to magnetic exchange coupling in polynuclear complexes has already been reviewed by Handrick et al 49 we only briefly restate the main features. The latter goes back to Anderson 38 and is also referred to as kinetic exchange as it originates from charge fluctuations between the two Fe 3d shells intermediate by the sulfur orbitals.…”

Section: Computational Detailsmentioning

confidence: 99%

Ab Initio Study of the Magnetic Coupling in Na₆Fe₂S₆

et al. 1997

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For the ternary thioferrate crystal Na 6 Fe 2 S 6 , ab initio quantum chemical calculations using a cluster model ansatz have been performed to examine the magnetic coupling of the two half-filled Fe 3d shells in the isolated dimeric [Fe 2 S 6 ] 6complexes having the structure of edge-linked double tetrahedra. The activeelectron approach using complete active space configuration interaction (CASCI) with 10 electrons in 10 orbitals yields the multiplet splitting of a two-center Heisenberg Hamiltonian with an antiferromagnetic coupling constant J ) -19 cm -1 , which is by a factor of 5 smaller than the experimental value. Correlation effects are essential for the magnetic coupling, as the application of multireference second-order Møller-Plesset perturbation theory based on the CIPSI algorithm (CAS-2nd) and the recently proposed difference-dedicated CI method lead to values J(4f5) ) -158 and -66 cm -1 , respectively, which clearly agree better with experiment. The different electronic contributions to the chemical bonding in the binuclear transition metal complex have been investigated using the constrained space orbital variation method.

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“…Hatfield et al studied dihalo-bridged Cu(II) dinuclear compounds and realized that the experimental coupling constant is correlated with the ɸ/R ratio, whereby ɸ is the Cu-Cl-Cu angle and R the longest Cu-Cl distance 15 . Although previous theoretical studies for this Cu(II) dinuclear compounds have been reported, there are still a wide range of aspects to be considered due to the large structural variety of this kind of material [16][17][18][19] . The most important factors, which have an influence on the coupling mechanism, are the connecting route of both copper atoms, the structure variations in the bridging region and nature of the terminal ligands 12 .…”

Section: Introductionmentioning

confidence: 99%

Interplay between structure and magnetism in the low-dimensional spin system: K(C₈H₁₆O₄)₂CuCl₃·H₂O

et al. 2017

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www.rsc.org/crystengcomm Materials based on a crown ether complex together with magnetic ions, especially Cu(II), can be used to synthesize new low dimensional quantum spin systems. We have prepared the new crown ether complex )-aquadichloro-copper(II)-potassium, K(C8H16O4)2CuCl3•H2O (1), determined its structure, and analyzed its magnetic properties. Complex (1) has a monoclinic structure and crystallizes in space group P21/n with the lattice parameters of a = 9.5976(5) Å, b = 11.9814(9) Å, c = 21.8713(11) Å and β = 100.945(4)°. The magnetic properties of this compound have been investigated in the temperature range 1.8 K -300 K. The magnetic susceptibility shows a maximum at 23 K, but no 3-D long range magnetic order down to 1.8 K. The S=1/2 Cu(II) ions form antiferromagnetically coupled dimers with Cu-Cl distances of 2. 2554(8) Å and 4.683(6) Å, and a Cu-Cl-Cu angle of 115.12(2)˚ with 2Jdimer= -2.96 meV (-23.78 cm -1 ). The influence of H2O on the Cl-Cu-Cl exchange path is analyzed. Our results show that the values of the singlet-triplet splitting are increasing considering H2O molecules in the bridging interaction. This is supported by Density functional theory (DFT) calculations of coupling constants with Perdew and Wang (PWC), Perdew, Burke and Ernzenrhof (PBE) and strongly constrained and appropriately normed (SCAN) exchange-correlation function show excellent agreement for the studied compound.

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Structural dependence of the singlet-triplet gap in doubly bridged copper dimers: a variational CI calculation

Cited by 61 publications

References 25 publications

Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

Ab Initio Study of the Magnetic Coupling in Na₆Fe₂S₆

Interplay between structure and magnetism in the low-dimensional spin system: K(C₈H₁₆O₄)₂CuCl₃·H₂O

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Structural dependence of the singlet-triplet gap in doubly bridged copper dimers: a variational CI calculation

Cited by 61 publications

References 25 publications

Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

Singlet-triplet energy gap in halogen-substituted carbenes and silylenes: a difference-dedicated configuration interaction calculation

Ab Initio Study of the Magnetic Coupling in Na6Fe2S6

Interplay between structure and magnetism in the low-dimensional spin system: K(C8H16O4)2CuCl3·H2O

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Product

Resources

About

Ab Initio Study of the Magnetic Coupling in Na₆Fe₂S₆

Interplay between structure and magnetism in the low-dimensional spin system: K(C₈H₁₆O₄)₂CuCl₃·H₂O