Contribution à l’étude des propriétés physiques de l’alliage CuCl1-xBrx (0≤ x ≤ 1) par la méthode FP - LMTO
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Date
2016-12-15
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Abstract
Résumé (Français et/ou Anglais) :
This work is a contribution to the study of structural, elastic, electronics, optics and thermodynamics, materials of the I-VII (copper halides) and the ternary alloy derived from these compounds, this summer to study by the muffin-tin orbital method linearized with a total potential (FP-LMTO) as part of the functional theory of DFT density, implemented in the code Mstudio Mindlab, and to determine the potential for exchange and correlation is used the approximations of the generalized gradient (GGA).
In this work, we have 1first ground state, the structural properties of CuX (CuCl, CuBr) after calculating the transition pressure we note that the most stable phase and the zinc-blende phase (B3) and vien computing elastic properties of binary compounds in their phase (B3). the lattice parameter, the elastic modulus and its derivative were calculated and compared, are in good agreement with experimental and other theoretical results. The elastic constants are close to the experimental data .
One of the most important aspects of our calculations is that brings out the important role played by the state (d) of the transition metal (Cu) which states p boron atom are absent. In the GGA approach, we studied the electronic properties (band structure, charge density and effective mass) of the parent compounds. The detailed study of the state total and partial density allowed us to determine the type of hybridization of the orbital and clarify the participation of each band in the link that give the good nature of the energy gap. The compounds exhibit a mixed character of ionic and covalent bonding and the semiconductor behavior to direct band gap Γ-Γ.
The elastic coefficients predicted by the model Mehl show that our materials are stable in this phase of zinc-blende structure and values are closest to the experiment.
Our study has established stability and physical properties of the CuCl1-x Brx alloy was used for the first time Züger technique to study the origin of the optical bowing. The chemical contribution (Charge) is more important than the structural effects and volumetric strain due to the small difference in ionicity Between the two parent compounds. The optical parameters are processed by code Mstudio Mindlab.
Quasi-harmonic Debye model, wherein the crystal vibrations are Treated as a continuum isotope obtained from derivative energy total electron relative to the volume.
This model provides results fundamentally correct and reasonable and in good agreement with experiment, we show that the coefficient of thermal expansion (α) increases with increasing temperature.
θD It is noted that decreases linearly with increasing temperature. For a fixed temperature, the Debye temperature increases with increasing pressure.
In conclusion, the dependencies of volume compressibility modulus, heat capacities and temperature on the Debye temperature and pressure were successfully obtained.
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Doctorat en Sciences
