Université de Fribourg

The electronic states of U⁴⁺ in U(PO₄)Cl: an example for angular overlap modeling of 5fⁿ systems

Bronova, Anna ; Bredow, Thomas ; Glaum, Robert ; Urland, Werner

In: Inorganic Chemistry, 2016, vol. 55, no. 14, p. 6853–6860

Detailed experimental data on UPO₄Cl comprising single-crystal UV/vis/NIR spectra and temperature-dependent magnetic susceptibilities form the basis for the investigation of the electronic structure of the U⁴⁺ cation in UPO₄Cl. For modeling of the observed physical properties the angular overlap model (AOM) was successfully employed. The computations were performed using the...

Université de Fribourg

Photoluminescence properties of Yb²⁺ ions doped in the perovskites CsCaX₃ and CsSrX₃ (X = Cl, Br, and I) – a comparative study

Suta, Markus ; Urland, Werner ; Daul, Claude ; Wickleder, Claudia

In: Physical Chemistry Chemical Physics, 2016, vol. 18, no. 19, p. 13196–13208

The Yb²⁺-doped perovskite derivatives CsMX₃ (M = Ca and Sr; X = Cl, Br, and I) are ideal systems for obtaining a detailed insight into the structure–luminescence relationship of divalent lanthanides. The investigation of the respective photoluminescence properties yielded two emission bands in the violet and blue spectral range for all compounds, which are assigned to the spin-allowed...

Université de Fribourg

Prospecting lighting applications with ligand field tools and density functional theory: a first-principles account of the 4f⁷–4f⁶5d¹ Luminescence of CsMgBr₃:Eu²⁺

Ramanantoanina, Harry ; Cimpoesu, Fanica ; Göttel, Christian ; Sahnoun, Mohammed ; Herden, Benjamin ; Suta, Markus ; Wickleder, Claudia ; Urland, Werner ; Daul, Claude

In: Inorganic Chemistry, 2015, vol. 54, no. 17, p. 8319–8326

The most efficient way to provide domestic lighting nowadays is by light-emitting diodes (LEDs) technology combined with phosphors shifting the blue and UV emission toward a desirable sunlight spectrum. A route in the quest for warm-white light goes toward the discovery and tuning of the lanthanide-based phosphors, a difficult task, in experimental and technical respects. A proper theoretical...

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

Flux Synthesis, Structure, Properties, and Theoretical Magnetic Study of Uranium(IV)-Containing A₂USi₆O₁₅ (A = K, Rb) with an Intriguing Green-to-Purple, Crystal-to-Crystal Structural Transition in the K Analogue

Morrison, Gregory ; Ramanantoanina, Harry ; Urland, Werner ; Smith, Mark D. ; Loye, Hans-Conrad zur

In: Inorganic Chemistry, 2015, vol. 54, no. 11, p. 5504–5511

Single crystals of uranium(IV)-containing A₂USi₆O₁₅ (A = K, Rb) were grown using the flux growth method. The two compounds crystallize in a new structure type related to Cs₂USi₆O₁₅. K₂USi₆O₁₅ exhibits an interesting crystal-to-crystal transition, which is accompanied by an intense color change. Magnetic properties are reported for A₂USi₆O₁₅ and differ from other...

Université de Fribourg

Tailoring the optical properties of lanthanide phosphors: prediction and characterization of the luminescence of Pr3+-doped LiYF4

Ramanantoanina, Harry ; Urland, Werner ; Herden, Benjamin ; Cimpoesu, Fanica ; Daul, Claude

In: Physical Chemistry Chemical Physics, 2015, vol. 17, no. 14, p. 9116–9125

We present a theoretical work detailing the electronic structure and the optical properties of (PrF₈)⁵⁻ embedded in LiYF₄, complementing the insight with data that are not available by experimental line. The local distortions due to the embedding of the lanthanide ion in the sites occupied in the periodic lattice by smaller yttrium centres, not detectable in regular X-ray analyses, are...

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

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

Ligand field density functional theory for the prediction of future domestic lighting

Ramanantoanina, Harry ; Urland, Werner ; García-Fuente, Amador ; Cimpoesu, Fanica ; Daul, Claude

In: Physical Chemistry Chemical Physics, 2014, vol. 16, no. 28, p. 14625–14634

We deal with the computational determination of the electronic structure and properties of lanthanide ions in complexes and extended structures having open-shell f and d configurations. Particularly, we present conceptual and methodological issues based on Density Functional Theory (DFT) enabling the reliable calculation and description of the f → d transitions in lanthanide doped phosphors. We...