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

Magnetic exchange interactions in Mn doped ZnSnAs₂ chalcopyrite

Bouhani-Benziane, H. ; Sahnoun, Omar ; Sahnoun, Mohammed ; Driz, Mohamed ; Daul, Claude A.

In: Journal of Magnetism and Magnetic Materials, 2015, vol. 396, p. 345–349

Accurate ab initio full-potential augmented plane wave (FP-LAPW) electronic calculations within generalized gradient approximation have been performed for Mn doped ZnSnAs₂ chalcopyrites, focusing on their electronic and magnetic properties as a function of the geometry related to low Mn-impurity concentration and the spin magnetic alignment (i.e., ferromagnetic vs antiferromagnetic). As...

Université de Fribourg

Development and applications of the LFDFT: the non-empirical account of ligand field and the simulation of the f–d transitions by density functional theory

Ramanantoanina, Harry ; Sahnoun, Mohammed ; Barbiero, Andrea ; Ferbinteanu, Marilena ; Cimpoesu, Fanica

In: Physical Chemistry Chemical Physics, 2015, vol. 17, no. 28, p. 18547–18557

Ligand field density functional theory (LFDFT) is a methodology consisting of non-standard handling of DFT calculations and post-computation analysis, emulating the ligand field parameters in a non-empirical way. Recently, the procedure was extended for two-open-shell systems, with relevance for inter-shell transitions in lanthanides, of utmost importance in understanding the optical and magnetic...

Université de Fribourg

Ab initio study of structural, electronic and thermodynamic properties of tungstate double perovskites Ba₂MWO₆ (M = Mg, Ni, Zn)

Sahnoun, Omar ; Bouhani-Benziane, H. ; Sahnoun, Mohammed ; Driz, Mohamed ; Daul, Claude A.

In: Computational Materials Science, 2013, vol. 77, p. 316–321

The structural and electronic properties of the double perovskite Ba₂MWO₆ with M = Mg, Ni, Zn have been studied using the full-potential linearized augmented plane wave (FP-LAPW) method by employing both the local density approximation (LDA) and the generalized gradient approximation (GGA), which are based on exchange–correlation energy optimization to calculate the total energy. Also we...

Université de Fribourg

Structural and electronic properties of isostructural transition metal nitrides

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

In: Physica B: Condensed Matter, 2010, no. 18, p. 3822-3825

The structural and electronic properties of three isostructural transition metal nitrides VN, NbN and TaN have been calculated using the full-potential linearized augmented plane-wave method within a generalized gradient approximation scheme for the exchange-correlation potential. Perfect NaCl structures as well as lattices containing nitrogen vacancies (M₄N₃), and an hexagonal ε-M₂N...

Université de Fribourg

Wavelet investigation of La0.5Ca0.5CoO3−δ x-ray absorption data

Sahnoun, Mohammed ; Daul, Claude A. ; Haas, O.

In: Journal of Applied Physics, 2007, vol. 101, no. 1, p. 014911

Morlet wavelet transformation was used to analyze the Co K-edge extended x-ray absorption spectrum of La0.5Ca0.5CoO3−δ. Due to recent success in wavelet analysis of extended x-ray absorption fine structure (EXAFS) data we hoped that the Co–La scattering path could be separated from the Co–Ca scattering path in the EXAFS spectrum of...

Université de Fribourg

Investigation of the electronic structure in La1-xCaxCoO₃ (x = 0, 0.5) using full potential calculations

Sahnoun, Mohammed ; Daul, Claude A. ; Haas, O. ; Wokaun, A.

In: Journal of Physics: Condensed Matter, 2006, vol. 17, p. 7995-8003

The electronic and magnetic properties of both LaCoO₃ and La0.5Ca0.5CoO₃ have been investigated by means of ab initio full-potential augmented plane wave plus local orbitals (APW+lo) calculations carried out with the Wien 2k code. The functional used is the local-density approximation LDA +U. Doping with Ca²⁺ introduces holes into the Co–O...

Université de Fribourg

Optical properties of germanium dioxide in the rutile structure

Sahnoun, Mohammed ; Daul, Claude A. ; Khenata, R. ; Baltache, H.

In: The European Physical Journal B, 2005, vol. 45(4), p. 455 - 458

We present first-principles calculations for the optical properties of germanium dioxide in the rutile structure. The electronic band structure has been calculated self-consistently within the local density approximation using the full-potential linearized augmented plane wave method. The electronic band structure shows that the fundamental energy gap is direct at the center of the Brillouin...

Université de Fribourg

Electronic structure and optical properties of TaC from the first principles calculation

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

In: The European Physical Journal B, 2005, vol. 44(3), p. 281

The electronic and optical properties of tantalum carbide TaC have been calculated using the full-potential linearized augmented-plane-wave method within the local density approximation scheme for the exchange-correlation potential. We find that the optical spectra can be extremely sensitive to the Brillouin zone sampling. The influence of relativistic effects on the dielectric function is...