DSpace 9 ENSET SKIKDA

Dépôt numérique de l'École Normale Supérieure de l’Enseignement Technologique – Skikda –

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Ab-initio Study of the Structural, Electronic, Optical, Thermal properties and Structural Stability of III-V ternary Semiconductors and double perovskites by the FP-LAPW
(Higher Normal School of Technological Education of Skikda, 2026) Louati, Nesrine; Oumelaz, fayçal
Through our work, we investigate the properties of YN1-xSbxternary alloys in which (Y: B, Al and Ga) while x represent the Sb concentration (x=0, 0.25, 0.5, 0.75 and 1) in addition to Sr2NaXO6 (X = Cl, Br, and I) double perovskites thought the Wien2k code package based on Density Functional Theory (DFT). This is achieved by full potential linearized augmented plane wave (FP-LAPW) method. A detailed and systematic analysis of the structural, electronic, optical, elastic and thermal properties in addition to thermoelectric properties for double oxide perovskite has been carried. Structural optimization, transition phase, thermal and elastic constant calculations were performed using the WC-GGA potential for YN1-xSbx alloys and PBEsol exchange–correlation functional forSr2NaXO6 (X = Cl, Br, and I) double perovskites. While the KTB-mBJ potential was employed to accurately, describe the electronic, thermoelectric, and optical properties. In addition, the WC-GGA and TB-mBJ scheme was used to further validate and refine the electronic band structure analysis. The elastic constants were calculated to verify the mechanical stability and determine the mechanical properties.The effect of temperature on the lattice constant, bulk modulus, heat capacity, and Debye temperature was also investigated. Our work demonstrates a high consistency between our calculated results and both available experimental data and previous theoretical studies. Therefore, we expect this research to represent a significant scientific contribution providing a valuable reference for future studies, as well as inspiring and facilitating subsequent experimental investigations
Etude chimique et activités biologiques des extraits bioactifs de l’inule visqueuse "Dittrichia viscosa" du Nord-Est Algérien
(École Normale Supérieure de l’Enseignement Technologique de Skikda, 2026) Mezi, Ilhem; Heni, Sonia
Cette étude vise à valoriser Dittrichia viscosa, une plante médicinale largement répandue dans le Nord-Est Algérien et couramment utilisée en médecine traditionnelle pour le traitement de diverses affections, en explorant de manière intégrée ses propriétés chimiques et biologiques. Pour cela, trois types de composés bioactifs ont été étudiés : l’huile essentielle, l’extrait méthanolique et l’extrait hydro-éthanolique, en combinant investigations phytochimiques, caractérisation chimique par GC-MS/MS et LC-MS/MS, essais biologiques in vitro ainsi que des approches in silico. Les activités antioxydante, anti-inflammatoire, antimicrobienne, antidiabétique, antifongique et cytotoxique ont été évaluées in vitro. Par ailleurs, des études d’amarrage moléculaire, complétées par des simulations de dynamique moléculaire ainsi que par des prédictions pharmacocinétiques et toxicologiques appliquées aux extraits, ont permis de conforter les données expérimentales et de mieux caractériser le potentiel pharmacologique de cette espèce. L’analyse chimique par GC-MS/MS de l’huile essentielle extraite a révélé la prédominance du cis-lancéol et du nérolidol, deux composés présentant un intérêt pharmacologique notable. Sur le plan antimicrobien, l’huile essentielle s’est montrée particulièrement efficace contre Staphylococcus aureus, Escherichia coli, Candida albicans et Bacillus cereus, tandis que Pseudomonas aeruginosa s’est révélée la souche la plus résistante. L’activité antiproliférative observée sur les cellules cancéreuses MCF-7 et les cellules normales L929 suggère toutefois un effet antiprolifératif modéré et non sélectif. Le profil de l’extrait méthanolique par LC-MS/MS a révélé une richesse notable en riboflavine et en acide chlorogénique, suggérant que Dittrichia viscosa pourrait représenter une source naturelle prometteuse de vitamine B2. Cet extrait a montré des activités biologiques significatives, incluant des effets antioxydants, anti-inflammatoires, antimicrobiens, antidiabétiques ainsi qu’une activité cytotoxique particulièrement notable sur la lignée cellulaire MCF-7. En revanche, son efficacité s’est révélée plus réduite à l’égard des champignons phytopathogènes. Par ailleurs, les investigations in silico réalisées dans le cadre des activités antioxydante, anti-inflammatoire, cytotoxique et antimicrobienne ont confirmé la stabilité des interactions entre plusieurs composés bioactifs et leurs cibles protéiques. Les analyses ADMET ont, quant à elles, mis en évidence des profils pharmacocinétiques globalement favorables, associés à une faible toxicité, renforçant ainsi l’intérêt pharmacologique de cet extrait. Par ailleurs, la caractérisation chimique de l’extrait hydro-éthanolique par LC-MS/MS a permis d’identifier onze composés bioactifs majeurs. Cet extrait a montré un effet notable sur la vvi majorité des activités biologiques étudiées dans les conditions in vitro. Les approches in silico ont particulièrement mis en évidence le rôle potentiel de la naringénine et de la rutine, qui présentent des interactions stables avec les protéines cibles COX-2 et Keap1, confirmées par des simulations de dynamique moléculaire et des calculs MM-PBSA
Structural Stability, Elecctronic, Opticol, and Thermal Properties of III-V Ternary Semiconductors: AxB1_xC
(Higher Normal School of Technological Education of Skikda, 2026) Chebouki, Sonia; Nemiri, Ouarda
First-principles simulations were carried out to explore the structural stability, electronic, optical, mechanical and thermal properties of InxAl1−xY semiconductor alloys (Y = N, P, As, Sb and Bi) using Density Functional Theory (DFT) based on the FP-LAPW method integrated in WIEN2k code. For exchange – correlation energy, the Wu–Cohen generalized gradient approximation (WC - GGA) was considered to examine structural and mechanical properties. In addition, modified Becke – Johnson potential proposed by Koller et al (nKTB - mBJ) along with the Engel – Vosko GGA, were utilized to refine the potential for accurate band structure analysis. Structural results confirm that all alloys stable in the zinc blende phase, except Y = N which favors the wurtzite structure, while lattice constants and bulk moduli follow Vegard’s law. Electronic analysis reveals indirect-to-direct band gap transitions with indium incorporation, improving optical performance and extending spectral coverage from the ultraviolet to the near - infrared region. Optical results indicate strong absorption in UV – visible for nitrides and phosphides, while heavier alloys shift absorption toward the infrared region. Mechanical calculations demonstrate elastic stability with brittle behavior. Thermal analyses show high Debye temperatures and thermal conductivities for compounds (N, P), while Sb - and Bi - based alloys exhibit lower conductivity, larger thermal expansion, and higher vibrational entropy, which make them favorable for thermoelectric applications. Overall, InxAl1−xY alloys combine strong structural stability, tunable band gaps, diverse optical responses, and promising thermal features, making them suitable for applications in LEDs, photodetectors, solar cells, and thermoelectric generators
Stusy of the Fundamental Properties of II-VI and III-V Semiconductor in the Framework of the DFT
(Higher Normal School of Technological Education of Skikda, 2026) Gouasmia, Wessem; Boudjaadar, Djamel
This thesis presents a first‑principles study of structural, stability, electronic, optical, elastic and thermal properties for four ternary alloys, the zinc-blende AlSb1−xAsx, AlSb1−xBix, and the rock‑ salt BaO1−xSx and BaO1−xSex at x = 0, 0.25, 0.50, 0.75, and 1. Energy-Volume data were fitted to Murnaghan E(V) establishing zinc‑blende and NaCl as the most stable phases. The enthalpy versus pressure study provides quantitative insight into the critical pressures associated with the phase transitions. The band structure and DOS calculations were carried out using the mBJ potential developed by Koller, Tran, and Blaha. AlSb1−xAsx ternary alloys exhibit a direct band gap Γ–Γ at x = 0.25 – 0.75. AlSb1−xBix have direct band gaps for all compositions with a nonzero concentration, the band gap decreases and extends from the near-infrared to the mid-infrared spectral range.The elastic constants were obtained using WC GGA/IRElast and Voigt-Reuss-Hill approaches. The optical spectra include the real and imaginary parts of the dielectric function, the refractive index, the absorption coefficient, and the reflectivity was investigated and discussed in detail. Thermal properties obtained from the Debye model reveal consistent trends linking atomic mass, chemical bonding, and lattice stiffness. Heat capacity shows the expected low-temperature rise and hightemperature saturation, the Debye temperature tracks lattice rigidity, the bulk modulus decreases with temperature, and the thermal expansion increases with temperature. The sodium chloride to cesium chloride transition pressures decrease with increasing chalcogen content and approach reported binary limits. Agreement with theoretical and experimental data for the binaries, together with consistency across properties, validates the used approaches. The thesis delivers a dataset of material properties across the compositions ( x). With newly reported elastic, optical, and thermal properties for compositions (x= 0.25, 0.5 and 0.75),in addition to identifying potential applications of these compounds, including light-emitting devices and photodetectors, as well as coatings and near-ultraviolet sensing devices
Synthesis and Characterization of Oxyuoride Glasses Doped With Rare-Earth Ions
(Higher Normal School of Technological Education of Skikda, 2026) Kinoucha, Khalida; Boubekri, Hani
This thesis investigates the synthesis and spectroscopic characterization of two lead germanate-based oxyfluoride glass systems: a ternary GPF matrix (GeO₂–PbO–PbF₂) co-doped with Tb³⁺/Yb³⁺ ions and a quaternary GPFC matrix (GeO₂–PbO–PbF₂–CdF₂) doped with Er³⁺ ions. The main objective is to evaluate their potential for photonic applications, particularly frequency conversion and optical amplification. The samples were synthesized using the melt-quenching method followed by annealing, and their amorphous nature was confirmed by X-ray diffraction (XRD). In the Tb³⁺/Yb³⁺ co-doped GPF system, luminescence studies reveal an up-conversion mechanism assisted by Yb³⁺ ions under near-infrared excitation. Power dependence measurements confirm a two-photon process involving cooperative energy transfer from Yb³⁺ to Tb³⁺ ions. In parallel, the Er³⁺-doped GPFC system was analyzed using the Judd–Ofelt formalism to determine the intensity parameters Ωt. The Ω₂ value (2.76 × 10⁻20 cm²) indicates significant local asymmetry and covalent character of the bonding environment. With a spectroscopic quality factor of 0.87 and a radiative lifetime of 4.31 ms for the ⁴I₁₃/₂ level, this glass exhibits strong potential for optical amplification in the C-band of optical communications (1530–1565 nm). These results highlight the strong potential of low-phonon-energy oxyfluoride glasses for advanced photonic devices and high-performance light sources.