|
| Titre : |
Ab initio Study of Some Physical Properties of the Cu2MgSiS4 and Cu2MgGeS4 diamond-like semiconductors and Sr2GeN2 Polymorphs |
| Type de document : |
texte imprimé |
| Auteurs : |
BEDJAOUI Abdelhak, Auteur |
| Editeur : |
Setif:UFA |
| Année de publication : |
2017 |
| Importance : |
1 vol (187 f .) |
| Format : |
29 cm |
| Langues : |
Français (fre) |
| Catégories : |
Thèses & Mémoires:Physique
|
| Mots-clés : |
Diamond-like compound
Sr2GeN2 polymorphs
First-principles calculations
structural parameters
Elastic moduli
Electronic structure Optical properties thermodynamic properties |
| Index. décimale : |
530 Physique |
| Résumé : |
In the present work, we have explored some physical properties of the two newly synthetized quaternary diamond-like
semiconductors Cu2MgSiS4 and Cu2MgGeS4, and two polymorphs of the ternary nitrides α-Sr2GeN2 and β-Sr2GeN2, using firstprinciple
calculations based on the density functional theory (DFT). The exchange-correlation effects were treated within the new
version of the generalized gradient approximation (GGA-PBEsol).
The structural, elastic, electronic and optical properties of the two considered diamond-like semiconductors were studied in
detail using two complementary first-principles approaches: the pseudopotential plane wave (PP-PW) and the full potential
augmented plane wane (FP-LAPW). The calculated equilibrium structural parameters are in good agreement with the available
experimental data. Single-crystal and polycrystalline elastic moduli and their related properties, including elastic constants, bulk
modulus, shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities
and Debye temperature, were predicted. We find that the inclusion of the electronic exchange-correlation through the newly
developed TB-mBJ improves the description of the electronic structure. The TB-mBJ yields a direct band gap (Γ-Γ) of 2.64 and
1.54 eV for Cu2MgSiS4 and Cu2MgGeS4, respectively. Frequency-dependence of the dielectric function, refractive index,
extinction coefficient, absorption coefficient, reflectivity, energy loss function and optical conductivity were predicted, and the
origins of the observed electronic transitions were assigned. Both Cu2MgSiS4 and Cu2MgGeS4 exhibit noticeable absorption in the
ultraviolet range.
The structural, elastic and thermodynamic properties of the α (tetragonal) and β (orthorhombic) polymorphs of the Sr2GeN2
compound have been examined in detail using ab initio pseudopotential plane-wave calculations. Apart the structural properties at
ambient conditions, all present reported results are predicted for the first time. The calculated equilibrium lattice parameters and
inter-atomic bond-lengths of the considered polymorphs are in good agreement with the available experimental data. It is found
that α-Sr2GeN2 is energetically more stable than β-Sr2GeN2. The two examined polymorphs are very similar in their crystal
structures and have almost identical local environments. The single-crystal and polycrystalline elastic parameters and related
properties, including elastic constants, bulk, shear and Young’s moduli, Poisson’s ratio, anisotropy indexes, Pugh’s criterion,
elastic wave velocities and Debye temperature, have been predicted. Temperature and pressure dependence of some macroscopic
properties - including the bulk modulus, volume thermal expansion coefficient, heat capacity and Debye temperature - have been
evaluated using ab initio calculations combined with the quasi-harmonic Debye model. |
| Côte titre : |
DPH/0207 |
| En ligne : |
https://drive.google.com/file/d/1znqhYjJAUf5xV_vYR8ftRwURwdDlL9eJ/view?usp=shari [...] |
| Format de la ressource électronique : |
pdf |
Ab initio Study of Some Physical Properties of the Cu2MgSiS4 and Cu2MgGeS4 diamond-like semiconductors and Sr2GeN2 Polymorphs [texte imprimé] / BEDJAOUI Abdelhak, Auteur . - [S.l.] : Setif:UFA, 2017 . - 1 vol (187 f .) ; 29 cm. Langues : Français ( fre)
| Catégories : |
Thèses & Mémoires:Physique
|
| Mots-clés : |
Diamond-like compound
Sr2GeN2 polymorphs
First-principles calculations
structural parameters
Elastic moduli
Electronic structure Optical properties thermodynamic properties |
| Index. décimale : |
530 Physique |
| Résumé : |
In the present work, we have explored some physical properties of the two newly synthetized quaternary diamond-like
semiconductors Cu2MgSiS4 and Cu2MgGeS4, and two polymorphs of the ternary nitrides α-Sr2GeN2 and β-Sr2GeN2, using firstprinciple
calculations based on the density functional theory (DFT). The exchange-correlation effects were treated within the new
version of the generalized gradient approximation (GGA-PBEsol).
The structural, elastic, electronic and optical properties of the two considered diamond-like semiconductors were studied in
detail using two complementary first-principles approaches: the pseudopotential plane wave (PP-PW) and the full potential
augmented plane wane (FP-LAPW). The calculated equilibrium structural parameters are in good agreement with the available
experimental data. Single-crystal and polycrystalline elastic moduli and their related properties, including elastic constants, bulk
modulus, shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities
and Debye temperature, were predicted. We find that the inclusion of the electronic exchange-correlation through the newly
developed TB-mBJ improves the description of the electronic structure. The TB-mBJ yields a direct band gap (Γ-Γ) of 2.64 and
1.54 eV for Cu2MgSiS4 and Cu2MgGeS4, respectively. Frequency-dependence of the dielectric function, refractive index,
extinction coefficient, absorption coefficient, reflectivity, energy loss function and optical conductivity were predicted, and the
origins of the observed electronic transitions were assigned. Both Cu2MgSiS4 and Cu2MgGeS4 exhibit noticeable absorption in the
ultraviolet range.
The structural, elastic and thermodynamic properties of the α (tetragonal) and β (orthorhombic) polymorphs of the Sr2GeN2
compound have been examined in detail using ab initio pseudopotential plane-wave calculations. Apart the structural properties at
ambient conditions, all present reported results are predicted for the first time. The calculated equilibrium lattice parameters and
inter-atomic bond-lengths of the considered polymorphs are in good agreement with the available experimental data. It is found
that α-Sr2GeN2 is energetically more stable than β-Sr2GeN2. The two examined polymorphs are very similar in their crystal
structures and have almost identical local environments. The single-crystal and polycrystalline elastic parameters and related
properties, including elastic constants, bulk, shear and Young’s moduli, Poisson’s ratio, anisotropy indexes, Pugh’s criterion,
elastic wave velocities and Debye temperature, have been predicted. Temperature and pressure dependence of some macroscopic
properties - including the bulk modulus, volume thermal expansion coefficient, heat capacity and Debye temperature - have been
evaluated using ab initio calculations combined with the quasi-harmonic Debye model. |
| Côte titre : |
DPH/0207 |
| En ligne : |
https://drive.google.com/file/d/1znqhYjJAUf5xV_vYR8ftRwURwdDlL9eJ/view?usp=shari [...] |
| Format de la ressource électronique : |
pdf |
|
Ajouter le résultat dans votre panier Affiner la recherche2021Synthèse, évaluation biologique et étude théorique de docking moléculaire de quelques aminophosphonates
Ab initio study of physical properties of some solid materials
