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Université de Fribourg

The choice of the exchange-correlation functional for the determination of the jahn–teller parameters by the density functional theory

Andjelković, Ljubica ; Gruden-Pavlović, Maja ; Daul, Claude ; Zlatar, Matija

In: International Journal of Quantum Chemistry, 2012, p. -

The Jahn–Teller (JT) parameters for small, aromatic, organic radicals, CnHn (n = 4–7), bis(cyclopentadienyl)cobalt(II) (cobaltocene), a sodium cluster (Na3), a silver cluster (Ag3), the hexaflurocuprate(II) ion ([CuF6]4−), and tris(acetylacetonato)manganese(III) ([Mn(acac)3]) have been evaluated by the means of the multideterminantal density functional theory using the most common...

Université de Fribourg

On exchange coupling and bonding in the Gd2@C80 and Gd2@C79N endohedral dimetallo-fullerenes

Cimpoesu, Fanica ; Frecus, Bogdan ; Oprea, Corneliu I. ; Ramanantoanina, Harry ; Urland, Werner ; Daul, Claude

In: Molecular Physics, 2015, vol. 113, no. 13-14, p. 1712–1727

A series of computational experiments performed with various methods belonging to wave-function and density functional theories approaches the issue of bonding regime and exchange coupling in the title compounds. Gd₂@C₈₀ is computed with a very weak exchange coupling, the sign depending on the method, while Gd₂@C₇₉N has resulted with a strong coupling and ferromagnetic ground state,...

Université de Fribourg

The theoretical account of the ligand field bonding regime and magnetic anisotropy in the DySc₂N@C₈₀ single ion magnet endohedral fullerene

Cimpoesu, Fanica ; Dragoe, Nita ; Ramanantoanina, Harry ; Urland, Werner ; Daul, Claude

In: Physical Chemistry Chemical Physics, 2014, vol. 16, no. 23, p. 11337–11348

Considering the DySc₂N@C₈₀ system as a prototype for Single Ion Magnets (SIMs) based on endohedral fullerenes, we present methodological advances and state-of-the art computations analysing the electronic structure and its relationship with the magnetic properties due to the Dy(III) ion. The results of the quantum chemical calculations are quantitatively decrypted in the framework of ligand...

Université de Fribourg

DFT study of mixed-valent Mn(II/III) hexacyanide clusters

Daul, Claude ; Rauzy, Cédrick ; Decurtins, Silvio ; Franz, Patrick ; Hauser, Andreas

In: International Journal of Quantum Chemistry, 2005, vol. 101 (6), p. 753-760

The cubic Prussian blue analogue Mn³[Mn(CN)₆]₂·15H₂O, which has the advantage of being transparent and magnetic (TN = 35 K) at the same time, has been investigated by density functional theory (DFT) calculations. The three-dimensional structure is built of MnII ions linked to MnIII ions by μ-bridging cyanides, to form a crystal structure,...

Université de Fribourg

Investigation of NLO properties of substituted (M)-tetrathia-[7]-helicenes by semiempirical and DFT methods

Daul, Claude ; Ciofini, Ilaria ; Weber, Valéry

In this article, we propose a theoretical study of static and dynamic polarizability α, first hyperpolarizability β, and second hyperpolarizability γ of substituted (M)-tetrathia-[7]-helicenes. Both a semiempirical approach, in the case of static and dynamic properties, and density functional theory, in the case of static electric properties, were used. The nonlinear optical (NLO) properties...

Université de Fribourg

Polytopal rearrangement of [Ni(acac)₂(py)]: A new square pyramid ⇄ trigonal bipyramid twist mechanism

Daul, Claude ; Niketic, Svetozar ; Rauzy, Cédrick ; Schläpfer, Carl-Wilhelm

In: Chemistry - A European Journal, 2004, vol. 10(3), p. 721-727

The interconversion mechanisms between three idealized polytopal forms (a square pyramid and two trigonal bipyramids) of [M(bidentate)₂(unidentate)] were investigated by an original combination of molecular mechanics (MM) and density functional theory (DFT) approaches. MM was used to model the mechanistic rearrangement path, and DFT to study selected points along this path. The test case was a...

Université de Fribourg

A ligand field theory-based methodology for the characterization of the Eu²⁺ [Xe]4f⁶5d¹ excited states in solid state compounds

García-Fuente, Amador ; Cimpoesu, Fanica ; Ramanantoanina, Harry ; Herden, Benjamin ; Daul, Claude ; Suta, Markus ; Wickleder, Claudia ; Urland, Werner

In: Chemical Physics Letters, 2015, vol. 622, p. 120–123

The theoretical rationalization of the open-shell 4f and 5d configuration of Eu²⁺ is by far not trivial because it involves a non-standard version of ligand field theory, based on a two-shell Hamiltonian. Here we present our methodology based on ligand field theory, taking the system CsCaBr₃:Eu²⁺ as a case study with an octahedral coordination sphere of Eu²⁺. The ligand field,...

Université de Fribourg

Photon cascade emission in Pr³⁺ doped fluorides with CaF₂ structure: Application of a model for its prediction

Herden, Benjamin ; García-Fuente, Amador ; Ramanantoanina, Harry ; Jüstel, Thomas ; Daul, Claude ; Urland, Werner

In: Chemical Physics Letters, 2015, vol. 620, p. 29–34

In this work, we predict and measure the optical behaviour of Pr³⁺ in different binary and ternary fluorides. We use a validated model based on Ligand Field Theory and Density Functional Theory to calculate the multiplet energy levels arising from the ground [Xe]4f² and excited [Xe]4f¹5d¹ electron configurations of Pr³⁺ in its chemical environment. Moreover, the luminescence spectra of...

Université de Fribourg

Electronic structure and magnetic properties of lanthanide 3+ cations

Kurzen, Helena ; Bovigny, Laura ; Bulloni, Claudio ; Daul, Claude

In: Chemical Physics Letters, 2013, vol. 574, p. 129–132

The magnetic properties of lanthanides are currently of great interest. Especially, the discovery that mononuclear complexes of rare earth (RE) ions can exhibit magnetic anisotropy and can act as single molecular magnets. Heretofore, the magnetic susceptibility of RE ions has often been estimated, using HUND’s empirical formula. In this work, we propose a non-empirical calculation of magnetic...

Université de Fribourg

Benzo[1,2-b:4,5-b′]difuran-based sensitizers for dye-sensitized solar cells

Li, Hui ; Yi, Chenyi ; Moussi, Sofiane ; Liu, Shi-Xia ; Daul, Claude ; Grätzel, Michael ; Decurtins, Silvio

In: RSC Advances, 2013, vol. 3, no. 43, p. 19798–19801

Two BDF-based organic sensitizers, as first examples for their use in dye-sensitized solar cells, are prepared and characterized. They yield promising power conversion efficiencies of up to 5.5% and high open circuit voltages up to 0.82 V. This work demonstrates that the BDF chromophore acts as an effective donor in organic sensitizers.