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Université de Fribourg

Calculation of spin-orbit coupling within the LFDFT: Applications to [NiX₄]²⁻ (X=F⁻, Cl⁻, Br⁻, I⁻)

Atanasov, Mihail ; Rauzy, Cédrick ; Baettig, Pio ; Daul, Claude A.

In: International Journal of Quantum Chemistry, 2005, vol. 102, p. 119-131

Spin-orbit coupling has been introduced into our newly developed ligand field density functional theory (LFDFT), using the zero-order regular approximation as implemented into the Amsterdam density functional (ADF) code. Application of the formalism to a series of NiX₄²⁻ (X=F⁻, Cl⁻, Br⁻, I⁻) compounds shows the increasing importance of intra-ligand spin-orbit coupling across the F,...

Université de Fribourg

Assessment of theoretical prediction of the NMR shielding tensor of ¹⁹⁵PtClxBr6–x²⁻ complexes by DFT calculations: experimental and computational results

Penka Fowe, Emmanuel ; Belser, Peter ; Daul, Claude A. ; Chermette, Henry

In: Physical Chemistry Chemical Physics, 2005, vol. 7(8), p. 1732-1738

In the present work, the ZORA spin–orbit Hamiltonian, in conjunction with the gauge including orbital (GIAO) method based on DFT theory has been used to calculate ¹⁹⁵Pt chemical shift of ¹⁹⁵PtClxBr6–x²⁻ complexes. Excellent agreement with experiments has been obtained for calculations bearing on optimized geometries and all electrons triple zeta +...

Université de Fribourg

Evaluation of two-electron integrals including the factors rk₁₂exp(−γr²₁₂) over Cartesian Gaussian functions

Weber, Valéry ; Daul, Claude A.

In: Computer Physics Communications, 2004, vol. 158 (1), p. 1-11

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...

Université de Fribourg

Hybrid ligand-field theory/quantum chemical calculation of the fine structure and ZFS in lanthanide(III) complexes

Borel, Alain ; Helm, Lothar ; Daul, Claude A.

In: Chemical Physics Letters, 2004, vol. 383 (5-6), p. 584-591

Ligand field effects in lanthanide ions compounds have consequences for optical and magnetic spectroscopy. In the analysis of electron paramagnetic resonance spectra of Gd³⁺ complexes, a major role is played by the zero field splitting (ZFS), which is a high order consequence of the ligand field and the spin–orbit coupling. We present a general parameterized method and a computer program for...

Université de Fribourg

Application of the density functional theory derived orbital-free embedding potential to calculate the splitting energies of lanthanide cations in chloroelpasolite crystals

Zbiri, Mohamed ; Atanasov, Mihail ; Daul, Claude A. ; Garcia-Lastra, Juan Maria ; Wesolowski, Tomasz A.

In: Chemical Physics Letters, 2004, vol. 397(4-6), p. 441-446

Ligand field splitting energies of lanthanides Ln³⁺ (Ln = from Ce to Yb) in octahedral environment are calculated using the Hohenberg–Kohn theorems based orbital-free embedding formalism. The lanthanide cation is described at orbital level whereas its environment is represented by means of an additional term in the Kohn–Sham-like one-electron equations expressed as an explicit functional...

Université de Fribourg

The calculation of ESR parameters by density functional theory: the g- and A-tensors of Co(acacen)

Atanasov, Mihail ; Baerends, Evert Jan ; Baettig, Pio ; Bruyndonckx, Raf ; Daul, Claude A. ; Rauzy, Cédrick ; Zbiri, Mohamed

In: Chemical Physics Letters, 2004, vol. 399(4-6), p. 433-439

The new DFT based ligand field (LF) model is proposed to calculate the g- and A-tensors of [Co(acacen)] that is known to be a difficult case. The results obtained are compared with the ZORA approach implemented in ADF as well as with the experimental values. The calculations are in good agreement with the experimental data and demonstrate the ability of the method to reproduce the large...

Université de Fribourg

FP-LAPW investigation of electronic structure of TaN and TaC compounds

Sahnoun, Mohammed ; Daul, Claude A. ; Driz, Mohamed ; Parlebas, J.C. ; Demangeat, C.

In: Computational Materials Science, 2005, vol. 33(1-3), p. 175-183

We study the structural and electronic properties of tantalum compounds, i.e. TaC and TaN, by means of accurate first principle total energy calculations using the full-potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method. The calculations are based on density functional theory and we use the local density approximation (LDA) as well as the generalized gradient...

Université de Fribourg

Full potential calculation of structural, electronic and optical properties of KMgF₃

Sahnoun, Mohammed ; Zbiri, Mohamed ; Daul, Claude A. ; Khenata, R. ; Baltache, H. ; Driz, M.

In: Materials Chemistry and Physics, 2005, vol. 91(1), p. 185-191

A theoretical study of the structural, electronic and optical properties of KMgF₃ is presented using the full-potential linearized augmented plane wave method (FP-LAPW). In this approach, the local density approximation was used for the exchange-correlation potentials. First, we present the main features of the structural and electronic properties of this compound, where the electronic band...

Université de Fribourg

Hydrogen bond stabilization in Diels–Alder transition states: The cycloaddition of hydroxy-ortho-quinodimethane with fumaric acid and dimethylfumarate

Tamilmani, Venkatachalam ; Daul, Claude A. ; Lage Robles, Jaime ; Bochet, Christian G. ; Venuvanalingam, P.

In: Chemical Physics Letters, 2005, vol. 406 (4-6), p. 355-359

DFT investigations on the mechanism of Diels–Alder reactions of a hydroxy-ortho-quinodimethane with fumaric acid derivatives were performed to understand the origin of the syn or anti configuration of the adducts. The diene hydroxyl group and the dieneophile carboxyl group show hydrogen bonding in the transition state, significantly favouring the syn product. This reaction is poorly...

Université de Fribourg

Chromatic Orthogonality in Organic Synthesis

Bochet, Christian G.

In: Synlett, 2004, p. 2268-2274

A major challenge in organic synthesis is the selective reaction of a functional group in the presence of others. This can be achieved by using an appropriate reagent, tuned to react exclusively at the desired center. An alternate approach would be to use a single reagent, and to transmit from the outside the information as to where it should react. This account describes the use of light as a...