PROPRIETES MAGNETIQUES DE NANOMATERIAUX : ETUDE PAR LA METHODE MONTE CARLO

This work presents the study of the magnetic and thermal properties of nanomaterials. We study the influence of the external magnetic field and the crystal field on the magnetic phase transitions, critical temperature, compensation temperature, magnetization, susceptibility and hysteresis cycles of these nano-systems by the Monte Carlo method with the Blume-Capel model. We discuss the effect of exchange coupling interactions and we determine phase diagrams at ground state in the following cases:- system built on a centered cubic structure with mixed spins.- spherical core-shell system. The shell sites are populated with probability p. - system composed of two magnetic bi-fullerene surfaces separated with non magnetic surfaces. The influence of the thickness of the non-magnetic surfaces, crystalline and external magnetic fields, and also the interaction RKKY, are discussed.- MnBi system. The effect of the number of layers on its magnetic properties and the hysteresis cycle are analyzed.Dans cette thèse, nous nous intéressons essentiellement à l’étude des propriétés magnétiques et thermiques de nano-systèmes. En se basant sur le modèle Blume-Capel, nous étudions l’influence du champ magnétique externe et du champ cristallin sur les transitions de phases magnétiques, la température critique, la température de compensation, l’aimantation, la susceptibilité et les cycles d’hystérésis de ces systèmes par la méthode Monte-Carlo. Par ailleurs, nous discutons l'effet des interactions de couplage d’échange et nous déterminons les diagrammes de phases à l'état fondamental dans les cas suivants :- système construit sur une structure cubique centrée avec des spins mixtes,- système cubique simple sphérique de type « core-shell » dont la couche externe est diluée,- système composé de deux surfaces magnétiques de type bi-fullerène séparées par des couches non magnétiques. L’influence de l’épaisseur des ces couches, des champs cristallin et magnétique externe et celle de l’interaction RKKY sont discutées,- structure MnBi. L'effet de l’épaisseur du système sur ses propriétés magnétiques et les cycles d'hystérésis sont analysés

Synthesis, spectroscopic characterization, X-Ray analysis, and DFT-HF calculations of 5-ethoxymethyl-8-hydroxyquinoline

5-ethoxymethyl-8-hydroxyquinoline was synthesized and characterized using spectroscopic methods (1 H, 13 C NMR, IR). The crystal structure determined at room temperature (295 K) by means of X-ray powder diffraction is orthorhombic, with space group Pbca and eight molecules per unit cell (Z = 8, Z 0 = 1). The lattice parameters are: a = 7.9551(12) A ˚ , b = 17.981(3) A ˚ , c = 15.125(2) A ˚ and V = 2163.5(6) A ˚ 3. Geometric parameters and properties depending on the charge distribution around the different types of donors and acceptors bonds within the molecule are calculated by density functional theory (DFT/B3LYP) and Hartree–Fock methods. Atomic charges and dipole moment value permit qualitative predictions about high reactivity of this molecule. The 5-ethox-ymethyl-8-hydroxyquinoline adopts a non-planar structure in the solid state and the molecule is stabilized by contact system as p–p stacking interactions, weak intra and intermolecular H-Bonding O–H...N and C–H...O types, this latter involving the rings of both adjacent molecules in plans with a gap from 0.638 A ˚

Synthesis, spectroscopic characterization, X-Ray analysis, and DFT-HF calculations of 5-ethoxymethyl-8-hydroxyquinoline

5-ethoxymethyl-8-hydroxyquinoline was synthesized and characterized using spectroscopic methods (1 H, 13 C NMR, IR). The crystal structure determined at room temperature (295 K) by means of X-ray powder diffraction is orthorhombic, with space group Pbca and eight molecules per unit cell (Z = 8, Z 0 = 1). The lattice parameters are: a = 7.9551(12) A ˚ , b = 17.981(3) A ˚ , c = 15.125(2) A ˚ and V = 2163.5(6) A ˚ 3. Geometric parameters and properties depending on the charge distribution around the different types of donors and acceptors bonds within the molecule are calculated by density functional theory (DFT/B3LYP) and Hartree–Fock methods. Atomic charges and dipole moment value permit qualitative predictions about high reactivity of this molecule. The 5-ethox-ymethyl-8-hydroxyquinoline adopts a non-planar structure in the solid state and the molecule is stabilized by contact system as p–p stacking interactions, weak intra and intermolecular H-Bonding O–H...N and C–H...O types, this latter involving the rings of both adjacent molecules in plans with a gap from 0.638 A ˚

Study of 5-azidomethyl-8-hydroxyquinoline structure by X-ray diffraction and HF-DFT computational methods

5-Azidomethyl-8-hydroxyquinoline has been synthesized and characterized using IR, 1 H and 13 C NMR spectroscopic methods. Thermal analysis revealed no solid-solid phase transitions. The crystal structure of this compound was refined by Rietveld method from powder X-ray diffraction data at 295 K. The single crystal structure of the compound at 260 K was solved and refined using SHELX 97 program. According to the data obtained by both methods, the structure of the compound is monoclinic, space group P2 1 /c, with Z = 4 and Z ' = 1. For the single crystal at 260 K, a = 12.2879 (9) Å, b = 4.8782 (3) Å, c = 15.7423 (12) Å, β=100.807(14)°. Mechanisms of deformation resulting from intra-and intermolecular interactions, such as hydrogen bonding, induced slight torsions in the crystal structure. The optimized molecular geometry of 5-azidomethyl-8-hydroxyquinoline in the ground state is calculated using density functional theory (B3LYP) and Hartree-Fock (HF) methods with the 6-311G(d,p) basis set. The calculated results show good agreement with experimental values. Energy gap of the molecule was found using HOMO and LUMO calculation which reveals that charge transfer occurs within the molecule