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Title: Modeling properties of molecules with open d-shells using density functional theory Author:Atanasov, Mihail Contributor:Daul, Claude A Date:
2005-08-08
Subject:density functional theory
- ligand-field theory
- spin–orbit coupling
- zero-field splitting
- magnetic exchange coupling Description:
An overview of the theory and applications of a recently proposed ligand-field density functional theory (LFDFT) is given. We describe a procedure based on DFT allowing to deduce the parameters of this non-empirical LF approach consisting of the following steps: (i) an average of configuration (AOC) DFT calculation, with equal occupancies of the d-orbitals is carried out (ii) with these orbitals kept frozen, the energies of all single determinants (SD) within the whole LF-manifold are calculated and used as a data base in a further step to provide all the Racah- and LF-parameters needed in a conventional LF-calculation. A more rigorous analysis of this approach in terms of Löwdin's energy partitioning and effective Hamiltonians is used to provide explicit context for its applicability and to set more rigorous criteria for its limitations. The formalism has been extended to account for spin-orbit coupling as well. Selected applications cover tetrahedral CrX₄ (X = Cl, Br) and FeO₄²⁻ and octahedral CrX₆³⁻ (X = F⁻, Cl⁻, Br⁻) complexes. Transition energies are calculated with an accuracy of 2000 cm⁻¹, deviations being larger for spin-forbidden transitions and smaller for spin-allowed ones. Analysis show, that ligand field parameters deduced from experiment are well reproduced, while interelectronic repulsion parameters are calculated systematically to be by 30–50% of lower in energy. A generalization of the LFDFT theory to dimers of transition metals allows to calculate exchange coupling integrals in reasonable agreement with experiment and with comparable success to the broken symmetry approach; in addition they allow to judge ferromagnetic contributions to exchange coupling integral which have been ignored before.
Linked entry:
Comptes Rendus Chimie. - 2005/8(9-10)//1421-1433
Host document:Comptes Rendus Chimie Identifier:
10.1016/j.crci.2005.04.003 (DOI)
Title: Improved coupled perturbed Hartree–Fock and Kohn–Sham convergence acceleration Author:Weber, Valéry Contributor:Daul, Claude A Date:
2003-04-07
Description:
A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree–Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some comparisons are presented and the method shows good convergences in almost all cases.
Linked entry:
Chemical Physics Letters. - 2003/370(1-2)//99-105
Host document:Chemical Physics Letters Identifier:
10.1016/S0009-2614(02)02025-0 (DOI)
Title: Multiplets of free d- and f-metal ions: A systematic DFT study Author:Borel, Alain Contributor:Daul, Claude A Date:
2006-04-02
Description:
In this work we apply in a systematic way our multi-determinantal model to calculate the fine structure of the whole atomic multiplet manifold. The key feature of this approach is the explicit treatment of near-degeneracy correlation using ad hoc configuration interaction (CI) within the active space of Kohn–Sham (KS) orbitals with open d- or f-shells. The calculation of the CI-matrices is based on a central symmetry decomposition of the energies of all single determinants (micro-states) calculated according to Density Functional Theory (DFT) for frozen KS-orbitals corresponding to the averaged configuration, eventually with fractional occupations, of the d- or f-orbitals and/or the direct calculation of the electrostatic reduced matrix elements (Racah or Slater–Condon parameters) occurring in the corresponding active space. We performed DFT calculations on all divalent and trivalent d²–d⁸ metal ions, as well as the f²–f¹² lanthanide(III) ions. We compare the results of both variants of the method with the data available in the literature. Both procedures yield multiplet energies with an accuracy of about hundred wave numbers and fine structure splitting accurate to less than a tenth of this amount.
Linked entry:
Journal of Molecular Structure: THEOCHEM. - 2006/762/1-3/93-10
Host document:Journal of Molecular Structure: THEOCHEM Identifier:
10.1016/j.theochem.2005.09.023 (DOI)
Title: Theoretical studies on the electronic properties and the chemical bonding of transition metal complexes using dft and ligand field theory Author:Atanasov, Mihail Contributor:Daul, Claude A Date:
2005
Subject:density functional theory
- electronic absorption and emission spectra
- ligand field theory
- magnetic-exchange coupling
- transition metal dimer complexes Description:
The research activity within our laboratory of computational chemistry at the University of Fribourg is presented. In this review, a brief outline of a recently proposed Ligand Field Density Functional Theory (LFDFT) model for single nuclear and its extension to dimer transition metal complexes is given. Applications of the model to dinuclear complexes are illustrated for the interpretation of exchange coupling in the bis-μ-hydroxo-bridged dimer of Cu(II) and to the description of the quadruple metal-metal bond in Re₂Cl₈²⁻. The analysis of the chemical bonding is compared with results obtained using other approaches, i.e. the Extended Transition State model and the Electron Localization Function. It is shown that the DFT supported Ligand Field Theory provides consistent description of the ground and excited state properties of transition metal complexes.
Linked entry:
Chimia. - 2005/59(7-8)//504
Host document:Chimia
Title: Calculation of ⁵⁹Co shielding tensor σ using LF–DFT Author:Senn, Florian Contributor:Daul, Claude A Date:
2010-03-01
Subject:Shielding tensor
- LF–DFT
- NMR
- ⁵⁹Co Description:
⁵⁹Co NMR shielding tensor σ calculation using perturbation theory within the framework of Ligand Field–Density Functional Theory (LF–DFT) [1] is implemented for transition-metal complexes as an extension of the LF–DFT methodology. We give some first results for absolute and relative shielding tensors, which are in a good agreement with experimental results as well as with other theoretical calculations.
Linked entry:
Journal of Molecular Structure: THEOCHEM. - 2010///-
Host document:Journal of Molecular Structure: THEOCHEM Identifier:
10.1016/j.theochem.2010.02.027 (DOI)
Title: Modeling properties of molecules with open d-shells using density functional theory Author:Atanasov, Mihail Contributor:Daul, Claude A Date:
2005-08-08
Subject:density functional theory
- ligand-field theory
- spin–orbit coupling
- zero-field splitting
- magnetic exchange coupling Description:
An overview of the theory and applications of a recently proposed ligand-field density functional theory (LFDFT) is given. We describe a procedure based on DFT allowing to deduce the parameters of this non-empirical LF approach consisting of the following steps: (i) an average of configuration (AOC) DFT calculation, with equal occupancies of the d-orbitals is carried out (ii) with these orbitals kept frozen, the energies of all single determinants (SD) within the whole LF-manifold are calculated and used as a data base in a further step to provide all the Racah- and LF-parameters needed in a conventional LF-calculation. A more rigorous analysis of this approach in terms of Löwdin's energy partitioning and effective Hamiltonians is used to provide explicit context for its applicability and to set more rigorous criteria for its limitations. The formalism has been extended to account for spin-orbit coupling as well. Selected applications cover tetrahedral CrX₄ (X = Cl, Br) and FeO₄²⁻ and octahedral CrX₆³⁻ (X = F⁻, Cl⁻, Br⁻) complexes. Transition energies are calculated with an accuracy of 2000 cm⁻¹, deviations being larger for spin-forbidden transitions and smaller for spin-allowed ones. Analysis show, that ligand field parameters deduced from experiment are well reproduced, while interelectronic repulsion parameters are calculated systematically to be by 30–50% of lower in energy. A generalization of the LFDFT theory to dimers of transition metals allows to calculate exchange coupling integrals in reasonable agreement with experiment and with comparable success to the broken symmetry approach; in addition they allow to judge ferromagnetic contributions to exchange coupling integral which have been ignored before.
Linked entry:
Comptes Rendus Chimie. - 2005/8(9-10)//1421-1433
Host document:Comptes Rendus Chimie Identifier:
10.1016/j.crci.2005.04.003 (DOI)
Title: Evaluation of two-electron integrals including the factors rk₁₂exp(−γr²₁₂) over Cartesian Gaussian functions Author:Weber, Valéry Contributor:Daul, Claude A Date:
2004-01-28
Subject:two-electron integrals
- damped-R12 integrals
- HGP recurrence relations Description:
We present a practical scheme for the evaluation of nonstandard two-electron integrals including the factors rk₁₂exp(−γr²₁₂) which have been appeared recently, where k>=-1 is an integer. The method used throughout this paper is based on the highly efficient Head-Gordon and Pople (HGP) approach of evaluation of electron repulsion integrals (ERI). Thus only straightforward modifications of existing codes that employ HGP or HGP-PRISM scheme are necessary to implement our approach.
Linked entry:
Computer Physics Communications. - 2004/158 (1)//1-11
Host document:Computer Physics Communications Identifier:
10.1016/S0010-4655(03)00497-1 (DOI)
Title: Improved coupled perturbed Hartree–Fock and Kohn–Sham convergence acceleration Author:Weber, Valéry Contributor:Daul, Claude A Date:
2003-04-07
Description:
A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree–Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some comparisons are presented and the method shows good convergences in almost all cases.
Linked entry:
Chemical Physics Letters. - 2003/370(1-2)//99-105
Host document:Chemical Physics Letters Identifier:
10.1016/S0009-2614(02)02025-0 (DOI)
Title: Investigating the M*He exciplexes, M = {Li,Na,K,Rb,Cs,Fr}: Density functional approach Author:Zbiri, Mohamed Contributor:Daul, Claude A Date:
2004
Description:
Potential curves for the ground and the first lowest excited states of the MHe (where M = {Li,Na,K,Rb,Cs,Fr}) exciplexes are calculated using the density functional theory (DFT) formalism. Relativistic calculations are carried out with and without spin-orbit (SO) coupling effect, using a zeroth order regular approximation (ZORA) approach. The depth De and position Re parameters of the potential curves for the case without spin-orbit effect are presented and compared with other works. Potential curves for Li-He, Cs-He, and Fr-He without spin-orbit effect and Cs-He with the spin-orbit effect are shown. A bond analysis is presented too, since the central interest of the study of the exciplexes is the nature and the existence of the bonding states that are the origin of emission spectra observed experimentally for these systems.
Linked entry:
Journal of Chemical Physics. - 2004/121(23)//11625-11628
Host document:Journal of Chemical Physics Identifier:
10.1063/1.1810133 (DOI)