M. GHEBOULI Mohamedamine

The Pseudopotential method coupled with plane waves implemented in the quantum espresso code
was used in the prediction of the structural parameters and elastic constants of SrCuX (X = P, Sb)
materials. The obtained results of lattice parameters and bulk modulus at equilibrium agree well with
their experimental and theoretical data cited in the literature. The calculated Young’s modulus of
SrCuX (X = P, Sb) aggregate thermoelectric materials are 109.25 GPa and 78.22 GPa, while their Debye
temperatures are 364.2 K and 261.8 K. The vibration energy of phonons is 24.14 kJ/mol and 23.37 kJ/
mol for SrCuP and SrCuSb. Our thermodynamic parameters increase monotonically with temperatures
for both SrCuP and SrCuSb materials. To the best of our knowledge, there are no data available in
the literature on the elastic and thermodynamic parameters of SrCuX (X = P, Sb) compounds, then
our results are prediction. The absence of virtual phonon frequencies indicates high dynamic stability
in both materials, with a band gap about 1 THz between optical and acoustic phonons in SrCuP and
SrCuSb

This prediction evaluates the different physical characteristics of magnetic materials X3FeO4 (X = Mg, Ca and Sr) by using density functional theory (DFT). The generalized gradient approximation (GGA) approach is chosen to define the exchange and correlation potential. The structural study of the compounds X3FeO4 (X = Mg, Ca and Sr) shows that the ferromagnetic phase is the more stable ground state, where all the parameters of the network are given at equilibrium. The calculated elastic constants confirm their stability in the cubic structure. The electronic characteristics calculated using the GGA and GGA + U approaches prove that all these compounds are semi-metallic with a wide band gap (EHM) and a high Curie temperature (TC). Furthermore, the magnetic moments of the studied compounds are calculated in order to claim their half-metallicity behavior. The p-d hybridization between the 3d-Fe and 2p-O states generates weak magnetic moments in the non-magnetic X and O sites, and decreases the Fe atomic moment relative to its free space charge of 4 µB. The thermal parameters including the thermal expansion coefficient, the heat capacity at constant volume and the Debye temperature were calculated for these compounds.

Density functional theory calculations were performed on the stability, mechanical, optoelectronic and thermoelectric characteristics for halide double perovskites (Cs2, K2, Rb2)SnCl6. This study focuses on the effects of temperature and chemical potential on electrons transport in these materials. Key transport results include maximum Seebeck coefficient of 1500 μVK⁻1 at 300 K, maximum power factor of 2.5 1011 Ws−1K−2 at 300 K and maximum electrical conductivity (σ/τ)x1019 Wm−1K−1s−1 of 11, 6 and 9 at 300 K for (Rb2, Cs2, K2)SnCl6. High Seebeck coefficient and high electrical conductivity prove the existence of covalent bonding between Cl-3p site and (Cs-6p, K-4S, Rb-5s) states with weak van der Waals type interactions, which is also confirmed by adsorption analysis. The charge transfer is taking place via Cl-3p and (Cs-6p, K-4S, Rb-5s) states between upper valence band and lower conduction band. The estimated power factor offers useful guidelines for tuning and improving the thermoelectric performance. The density of states predicts the n-type conductivity in all compounds which was confirmed from positive value of Seebeck coefficient.

Density functional theory calculations were performed on the stability, mechanical, optoelectronic and ther-
moelectric characteristics for halide double perovskites (Cs2, K2, Rb2)SnCl6. This study focuses on the effects of
temperature and chemical potential on electrons transport in these materials. Key transport results include
maximum Seebeck coefficient of 1500 μVK⁻1 at 300 K, maximum power factor of 2.5 1011 Ws 1K 2 at 300 K and
maximum electrical conductivity (σ/τ)x1019 Wm 1K 1s 1 of 11, 6 and 9 at 300 K for (Rb2, Cs2, K2)SnCl6. High
Seebeck coefficient and high electrical conductivity prove the existence of covalent bonding between Cl-3p site
and (Cs-6p, K-4S, Rb-5s) states with weak van der Waals type interactions, which is also confirmed by adsorption
analysis. The charge transfer is taking place via Cl-3p and (Cs-6p, K-4S, Rb-5s) states between upper valence band
and lower conduction band. The estimated power factor offers useful guidelines for tuning and improving the
thermoelectric performance. The density of states predicts the n-type conductivity in all compounds which was
confirmed from positive value of Seebeck coefficient.

The objective of this paper is to provide a comprehensive overview of optimal control models in the context of cancer treatment. We will explore how these mathematical models are used to optimize the administration of anticancer drugs. By understanding the principles behind optimal control models, we can appreciate their potential to revolutionize cancer treatment and contribute to personalized medicine. We utilize recent advancements in dynamic programming method to achieve a rigorous solution for a cancer disease model proposed by Neilan as an unsolved problem. Beginning with a certain refinement of Cauchy's method of characteristics for stratified Hamilton–Jacobi equations allows us to delineate a broad range of admissible trajectories. This, in turn, leads to the identification of a domain wherein the value function not only exists but is also generated by a certain admissible control. While the optimality is checked by using one of the well-known verification theorems taken as sufficient optimality conditions.

Lead-based double perovskites are studied in the cubic phase using the generalized gradient approximation and the modified Becke–Johnson (mBJ-GGA) functionals as implemented in the Wien2K code. Goldschmidt tolerance factor and octahedral factor, formation enthalpy, and formation energy translate the structural, chemical, and thermodynamic stability of double perovskites studied. Phonon band structures and elastic moduli ensure the dynamic and mechanical stability of (Cs2, K2, Rb2)PbCl6. An intermediate band appears in the conduction band and the fundamental transition takes place between 3p-Cl state and 6p-Pb site. The refractive index of double perovskites (Cs2, K2, Rb2)PbCl6 in the visible and ultraviolet light hold a huge advantage for solar cell applications. The wide dielectric constant of double perovskites under study makes them capable for absorbing energy between 1 and 5 eV, and are suitable for solar power applications. (Cs2, K2, Rb2)PbCl6 have positive Seebeck coefficient, which reveals that p-type charge carriers are dominant for enhancing their performance. Cs2PbCl6 has positive thermal conductivity for both n-type and p-type character. (K2, Rb2)PbCl6 have positive thermal conductivity for n-type character. The complete analysis reveals that they are potentially significant candidates for future solar cells and energy harvesting devices.

First-principle calculations using the Wien2k code and the GGA-mBJ exchange potential were used in the study of the thermodynamic, dynamic, chemical and elastic stability, as well as the electronic, optical and thermoelectric properties of Cs2(Sn, Pt, Te)I6. The presence of an intermediate band in Cs2(Sn, Pt, Te)I6 semiconductors confirmed by absorption peaks appeared at photon energy corresponding to the band gap enhances the efficiency of solar cells. The ideal band gap, high dielectric constants and optimal absorption make the double perovskites under study perform well in solar cells. The calculated minimum formation energy, Helmholtz free energy and phonon modes through the first Brillouin zone for the investigated Cs2(Sn, Pt, Te)I6 family confirm their thermal, thermodynamic and dynamic stability. The acoustic phonon contribution modes come from the Cs-6s and I-5p electrons, while the Pt-6s, Sn-5p, Te-5p and I-5p electrons participate in the optical phonon modes. The narrowness of the upper valence band and the band gap in the visible region for advantage this double perovskite in energy harvesting. The geometric Goldschmidt tolerance factor value between 0.8 and 1.0 and octahedral factor 0.41 indicate that double perovskite is more stable.

This work investigates the mechanical properties of B2-type CoTi material, using the density func-
tional theory within the pseudopotential method and a plane waves basis set as implemented in the Quantum
Espresso code. Our calculation yielded values of Debye temperature θD = 414.6 K and elastic constants
C11 = 226.50 GPa, C12 = 129.55 GPa, and C44 = 226.50 GPa, respectively. To test the incertitude of calculated
elastic constants Cij for B2-type CoTi intermetallic compound, we compared our obtained results with the
experimental values of the literature. Our findings show a good agreement with experimental data. Further-
more, using an approximation based on the quasi-harmonic model, we explore various thermodynamic
properties of the B2-type CoTi intermetallic compound. The thermodynamic properties obtained in this
study reveal that the free energy decreases gradually with the augmentation of the temperature, while both the
heat capacity as well as the entropy increase with the raising of the temperature. At T = 298 K, our calculation
yielded values of entropy S = 68.35 J mol –1 K –1 and heat capacity CV = 46.61 J mol –1 K –1
, respectively. To
the authors’ knowledge, no previous study has reported theoretical data on the thermodynamic properties for
CoTi material

This paper studies a novel surface plasmon resonance (SPR) biosensor using a BK7 glass prism, a copper (Cu)
metal plasmonic layer, which combine a halide perovskite (FASnI3) with two-dimensional (2D) materials such as
phosphorus black, graphene and TMDC (MoS2, MoSe2, WS2, WSe2) for the detection of breast cancer cells. We
have optimized the thickness of each layer in order to obtain maximum sensitivity. A numerical study mainly
uses the transfer matrix principle, while the attenuation total reflection method involves examining the reflection
properties. The evaluation of SPR biosensor configurations serves to obtain optimal performance. The simulation
results indicate that the integration of halide perovskite (FASnI3) and 2D materials into the BK7/Cu/medium
sensing structure significantly improves the sensitivity and figure of merit (ZT). The outstanding results in terms
of sensor performance characteristics are observed in the BK7/Cu (48 nm)/FASnI3 (5 nm)/BP (0.53 nm)
configuration. The figure of merit and sensitivity estimated at 123.11 RIU− 1 and 459.28◦/RIU, with a notable
improvement of 338.45 %.

Hybrid organic, halide, and divalent metal double perovskites were computed in the cubic structure using GGA and mBJ-GGA functionals. Goldschmidt tolerance factor and octahedral factor, Helmholtz free energy and formation energy translate the structural, chemical and thermodynamic stability of compounds studied. The equilibrium lattice constant for and deviates from the experimental value by 4.3% and 3.1%. Elastic constants are significantly smaller due to their larger reticular distances and lower Coulomb forces and hardness. The high dynamic lattice anharmonicity reduces their electronic conductivity, which gives them a usage advantage in the thermoelectric field. predict the indirect band gap X-L nature, while that of is direct Γ-Γ. The band gap in the visible region provides an advantage for the energy harvesting property. The electronic transition in double perovskites under study takes place between Br-4p and K-4s orbitals. Hybrid organic-inorganic
halide perovskites are excellent semiconductors

We analyse a detailed investigation of structure, electronic, optical, magnetic and thermoelectric properties of
(Cs, Rb, K)2MnF6 double perovskites with cubic Fm3m space group. The calculation method was the augmented
plane-wave functions plus local orbitals as implemented in the WIEN2k code and the GGA followed by the most
accurate GGA-mBJ as exchange potentials. The precision of our K2MnF6, Rb2MnF6 and Cs2MnF6 lattice constant
compared with their available experimental data is in the range 1.2 % to 3.6 %. The calculated band gap of
K2MnF6, Rb2MnF6 and Cs2MnF6 materials advantages them for use in light-emitting diode technology. These
materials exhibit ferromagnetic behavior. The negative formation energy, free Helmholtz energy and the
dispersion of phonons confirm their thermal, thermodynamic and dynamic stability. The calculated band gap of
K2MnF6, Rb2MnF6 and Cs2MnF6 materials advantages them for use in light-emitting diode technology. The p-type
charge carriers, direct band gap, and flat conduction and valence bands make them as good thermoelectric
materials. The major contribution to the magnetization comes from the unfilled Mn-3d orbital. The high static
dielectric constant reduces the recombination rate of charge carriers and the presence of absorption peaks in the
ultraviolet region are advantageous in the exploitation in the optoelectronic field. The flat valence and conduction bands, high p-type conductivity, good thermoelectric parameters, as well as non-toxicity make these
compounds mainly attractive in the thermoelectric application.

First-principle calculations using the Wien2k code and the GGA-mBJ exchange potential were used in the study
of the thermodynamic, dynamic, chemical and elastic stability, as well as the electronic, optical and thermoelectric properties of Cs2(Sn, Pt, Te)I6. The presence of an intermediate band in Cs2(Sn, Pt, Te)I6 semiconductors
confirmed by absorption peaks appeared at photon energy corresponding to the band gap enhances the efficiency
of solar cells. The ideal band gap, high dielectric constants and optimal absorption make the double perovskites
under study perform well in solar cells. The calculated minimum formation energy, Helmholtz free energy and
phonon modes through the first Brillouin zone for the investigated Cs2(Sn, Pt, Te)I6 family confirm their thermal,
thermodynamic and dynamic stability. The acoustic phonon contribution modes come from the Cs-6s and I-5p
electrons, while the Pt-6s, Sn-5p, Te-5p and I-5p electrons participate in the optical phonon modes. The
narrowness of the upper valence band and the band gap in the visible region for Cs2PtI6 advantage this double
perovskite in energy harvesting. The geometric Goldschmidt tolerance factor value between 0.8 and 1.0 and
octahedral factor 0.41 indicate that Cs2SnI6 double perovskite is more stable.

The molecular structures of WCl6, WCl5, WCl4, WCl3 have been optimized by density functional theory calculations. We report the stability of the phases in the ground state, the total energies and the optoelectronic
properties of the W-Cl system. We find that the material having a low tungsten concentration shows a low DOS at
the Fermi level, which implies a high resistivity. Both polymorphs of WCl6 are crystalline solids at room temperature and show the (α- WCl6) and (β- WCl6) phases of space group R-3 and P-3 m1 observed at 228 ◦C. The
change in temperature influences the structural, electronic and optical properties. The object of this paper does
not concern only the study of all phases, but also one controls the physical states of the molecular materials when
they are subjected to polymorphic changes. Calculations on the molecular structure under symmetry indicated an
orbitally degenerate ground state with bond distances in good agreement with experiment.

We analyse a detailed investigation of structure, electronic, optical, magnetic and thermoelectric properties of (Cs, Rb, K)2MnF6 double perovskites with cubic space group. The calculation method was the augmented plane-wave functions plus local orbitals as implemented in the WIEN2k code and the GGA followed by the most accurate GGA-mBJ as exchange potentials. The precision of our K2MnF6, Rb2MnF6 and Cs2MnF6 lattice constant compared with their available experimental data is in the range 1.2 % to 3.6 %. The calculated band gap of K2MnF6, Rb2MnF6 and Cs2MnF6 materials advantages them for use in light-emitting diode technology. These materials exhibit ferromagnetic behavior. The negative formation energy, free Helmholtz energy and the dispersion of phonons confirm their thermal, thermodynamic and dynamic stability. The calculated band gap of K2MnF6, Rb2MnF6 and Cs2MnF6 materials advantages them for use in light-emitting diode technology. The p-type charge carriers, direct band gap, and flat conduction and valence bands make them as good thermoelectric materials. The major contribution to the magnetization comes from the unfilled Mn-3d orbital. The high static dielectric constant reduces the recombination rate of charge carriers and the presence of absorption peaks in the ultraviolet region are advantageous in the exploitation in the optoelectronic field. The flat valence and conduction bands, high p-type conductivity, good thermoelectric parameters, as well as non-toxicity make these compounds mainly attractive in the thermoelectric application.

First-principle calculations using the Wien2k code and the GGA-mBJ exchange potential were used in the study of the thermodynamic, dynamic, chemical and elastic stability, as well as the electronic, optical and thermoelectric properties of Cs2(Sn, Pt, Te)I6. The presence of an intermediate band in Cs2(Sn, Pt, Te)I6 semiconductors confirmed by absorption peaks appeared at photon energy corresponding to the band gap enhances the efficiency of solar cells. The ideal band gap, high dielectric constants and optimal absorption make the double perovskites under study perform well in solar cells. The calculated minimum formation energy, Helmholtz free energy and phonon modes through the first Brillouin zone for the investigated Cs2(Sn, Pt, Te)I6 family confirm their thermal, thermodynamic and dynamic stability. The acoustic phonon contribution modes come from the Cs-6s and I-5p electrons, while the Pt-6s, Sn-5p, Te-5p and I-5p electrons participate in the optical phonon modes. The narrowness of the upper valence band and the band gap in the visible region for advantage this double perovskite in energy harvesting. The geometric Goldschmidt tolerance factor value between 0.8 and 1.0 and octahedral factor 0.41 indicate that double perovskite is more stable.

Effect of functional on structural, elastic, optoelectronic and thermoelectric characteristics of semiconducting
MgX2Se4 (X = Lu, Y) spinels has been realized by WIEN2k code. The lattice constant of MgY2Se4 is slightly greater
than that of MgLu2Se4, and these quantities are slightly deviated from the experimental values, where the error does not
exceed 1.3%. The cohesive energy proves that both spinels are chemically stable in the normal case, and this stability is
more pronounced in MgLu2Y4. The large ionic radius of Lu compared to Y explains the high bulk modulus of MgY2Se4 as
well as its hardness. The spinels under study have U ? U direct band gap located between 1.178 and 1.4 eV for all the
functionals, proving their semiconductor nature. Se-s, Y-d, Lu-d states in MgY2Se4 and MgLu2Se4 dominate the upper
valence band, while the first conduction band located between Fermi level and 1.5 eV is empty. There is a strong coupling
between Se-p–Lu-p sites for MgLu2Se4 and Se-p–Y-p states in MgY2Se4, which reflects their hybridization. The high
absorption in the ultraviolet range, the band gap between 1 and 2.4 eV and the refractive index in the range of 2.29–2.61
favour these spinels as absorbers in solar cells. Peaks of all the optical quantities studied relating to the mBJ–GGA
functional are shifted to the right compared with GGA and GGA?SO approximations. The thermoelectric parameters
were investigated as a function of photon energy and temperature using GGA?SO functional.

This study investigated the synthesis and analysis of Co–Zn nanoferrites, specifically Co0.6Zn0.4Fe2O4, using the sol–gel
method. The morphological, structural, and electrical properties of these ferrites were explored. The Co0.6Zn0.4Fe2O4 spinel
ferrite was synthesized using metal nitrate reagents and ethylene glycol, followed by a series of heating and sintering
processes. Rietveld-refined X-ray diffraction (XRD) confirmed the crystalline structure and phase purity, revealing a
monophasic spinel structure. Scanning electron microscopy (SEM) analysis showed distinct grain agglomeration and
porosity, indicating the material’s unique microstructure. Impedance measurements further characterized the optical and
electrical properties. The electrical conductivity of Co0.6Zn0.4Fe2O4 demonstrated a thermally activated conduction process,
adhering to Jonscher’s universal power law. The complex impedance analysis revealed thermally activated behavior,
confirming the presence of relaxation processes influenced by temperature. Nyquist plots indicated the contributions of
grains, grain boundaries, and electrodes to the electrical behavior. The complex electrical modulus and dielectric studies
provided insights into the dielectric characteristics, confirming high space charge polarization at grain boundaries and low
dielectric loss. These findings suggested that Co0.6Zn0.4Fe2O4 nanoferrites synthesized via the sol–gel method exhibited
desirable electrical and structural properties, making them promising for various technological applications.

Effect of functional on structural, elastic, optoelectronic and thermoelectric characteristics of semiconducting MgX2Se4 (X = Lu, Y) spinels has been realized by WIEN2k code. The lattice constant of MgY2Se4 is slightly greater than that of MgLu2Se4, and these quantities are slightly deviated from the experimental values, where the error does not exceed 1.3%. The cohesive energy proves that both spinels are chemically stable in the normal case, and this stability is more pronounced in MgLu2Y4. The large ionic radius of Lu compared to Y explains the high bulk modulus of MgY2Se4 as well as its hardness. The spinels under study have Г → Г direct band gap located between 1.178 and 1.4 eV for all the functionals, proving their semiconductor nature. Se-s, Y-d, Lu-d states in MgY2Se4 and MgLu2Se4 dominate the upper valence band, while the first conduction band located between Fermi level and 1.5 eV is empty. There is a strong coupling between Se-p–Lu-p sites for MgLu2Se4 and Se-p–Y-p states in MgY2Se4, which reflects their hybridization. The high absorption in the ultraviolet range, the band gap between 1 and 2.4 eV and the refractive index in the range of 2.29–2.61 favour these spinels as absorbers in solar cells. Peaks of all the optical quantities studied relating to the mBJ–GGA functional are shifted to the right compared with GGA and GGA+SO approximations. The thermoelectric parameters were investigated as a function of photon energy and temperature using GGA+SO functional.

In this comprehensive study, we synthesized Co0.6Zn0.4Fe2O4 cubic spinel via the sol–gel method and characterized its
structural, thermal, and optical properties. X-ray diffraction (XRD) verified the crystallization within the cubic Fd-3 m space
group, and a detailed analysis determined a crystallite size ranging from 47 to 58 nm. Notably, the calculated crystallite
size of 49.4 nm revealed inherent limitations in Scherer’s formula, which does not account for intrinsic strain effects from
crystal defects, grain boundaries, and stacking. Optical investigations, utilizing UV–Vis absorption spectroscopy, unveiled
a direct optical band gap of 1.26 eV, suggesting semiconductor behavior. The material’s thermal conductivity was found to
be highly temperature sensitive, reaching its maximum value for both spin orientations at 900 K, with a quantified value of
ke/τ = 4 × 1014 W/(mKs). This thermal behavior, along with the observed disorder (Eu value of 1.41 eV) and higher Urbach
energy, offers valuable insights into the material’s response under varying temperature conditions, essential for applications
in diverse technological domains.

Hybrid organic-inorganic double perovskites have garnered significant attention as promising materials for solar energy applications due to their tunable optoelectronic properties, structural versatility, and potential for low-cost fabrication. In this work, we explore the structural, electronic, and optical properties of K2(Sn,Pt,Te)Br6 hexahalometallate single crystals using a combination of experimental synthesis and first-principles density functional theory (DFT) calculations. The synthesized single crystals exhibit a cubic double perovskite structure with high crystallinity and stability, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electronic band structure calculations reveal direct and indirect bandgaps in the visible range, making these materials suitable for efficient light absorption in solar cells. The presence of organic cations in the hybrid structure enhances charge carrier mobility and reduces recombination losses, as evidenced by photoluminescence (PL) and time-resolved spectroscopy. Optical absorption measurements demonstrate strong absorption coefficients in the ultraviolet-visible (UV-Vis) region, highlighting their potential for photovoltaic applications. Additionally, the thermal stability and defect tolerance of K2(Sn,Pt,Te)Br6 perovskites are investigated, showing excellent resistance to environmental degradation. Our findings suggest that these hybrid hexahalometallate double perovskites are promising candidates for next-generation solar energy technologies, offering a pathway toward high-efficiency, low-cost, and stable photovoltaic devices.

Effect of functional on structural, elastic, optoelectronic and thermoelectric characteristics of semiconducting MgX2Se4 (X = Lu, Y) spinels has been realized by WIEN2k code. The lattice constant of MgY2Se4 is slightly greater than that of MgLu2Se4, and these quantities are slightly deviated from the experimental values, where the error does not exceed 1.3%. The cohesive energy proves that both spinels are chemically stable in the normal case, and this stability is more pronounced in MgLu2Y4. The large ionic radius of Lu compared to Y explains the high bulk modulus of MgY2Se4 as well as its hardness. The spinels under study have Г → Г direct band gap located between 1.178 and 1.4 eV for all the functionals, proving their semiconductor nature. Se-s, Y-d, Lu-d states in MgY2Se4 and MgLu2Se4 dominate the upper valence band, while the first conduction band located between Fermi level and 1.5 eV is empty. There is a strong coupling between Se-p–Lu-p sites for MgLu2Se4 and Se-p–Y-p states in MgY2Se4, which reflects their hybridization. The high absorption in the ultraviolet range, the band gap between 1 and 2.4 eV and the refractive index in the range of 2.29–2.61 favour these spinels as absorbers in solar cells. Peaks of all the optical quantities studied relating to the mBJ–GGA functional are shifted to the right compared with GGA and GGA+SO approximations. The thermoelectric parameters were investigated as a function of photon energy and temperature using GGA+SO functional.

First-principle calculations using the Wien2k code and the GGA-mBJ exchange potential were used in the study of the thermodynamic, dynamic, chemical and elastic stability, as well as the electronic, optical and thermoelectric properties of Cs2(Sn, Pt, Te)I6. The presence of an intermediate band in Cs2(Sn, Pt, Te)I6 semiconductors confirmed by absorption peaks appeared at photon energy corresponding to the band gap enhances the efficiency of solar cells. The ideal band gap, high dielectric constants and optimal absorption make the double perovskites under study perform well in solar cells. The calculated minimum formation energy, Helmholtz free energy and phonon modes through the first Brillouin zone for the investigated Cs2(Sn, Pt, Te)I6 family confirm their thermal, thermodynamic and dynamic stability. The acoustic phonon contribution modes come from the Cs-6s and I-5p electrons, while the Pt-6s, Sn-5p, Te-5p and I-5p electrons participate in the optical phonon modes. The narrowness of the upper valence band and the band gap in the visible region for advantage this double perovskite in energy harvesting. The geometric Goldschmidt tolerance factor value between 0.8 and 1.0 and octahedral factor 0.41 indicate that double perovskite is more stable.

Some physical properties of hexahalometallate were computed in the zinc blend structure using GGA-PBESOL. The cell constant is consistent to the experiment value quoted in the literature, where the error is 0.95% and 1%. The elastic constants of hexahalometallate compounds are significantly smaller due to their larger reticular distances, lower Coulomb forces and then they are soft and damage tolerant. The internal coordinate of Br atom in K2PtBr6 is lower than that of the same atom in K2SnBr6, and this can be explained by the fact that it is inversely proportional to the atom radius of Se and Pt. There are two major plasmonic processes, with intensities 3.7 and 1.35 located around 53.5 nm and 72.8 nm for K2SnBr6 and K2PtBr6.

The Quaternary Heusler alloys CoFeXAs (X = Cr, Mn and V) fully spin-polarized with half-metallic stability, show low direct band gap, high absorption in the ultraviolet light, high spin polarization and adequate Seebeck coefficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 μB, 5 μB and 3 μB according to the Slater-Pauling rule. The obtained minimal energy favors the type I CoFeVAs alloy over the type III CoFeCrAs and CoFeMnAs alloys. For CoFeCrAs and CoFeMnAs alloys, there is no band gap close to the Fermi level in the minority-spin, suggesting that they are direct Г–Г band gap semiconductors. Three-dimensional Co, Fe, and Mn atoms hybridized strongly, with little input from V and As atoms. Co, Fe, Cr, and Mn all have parallel magnetic moments, which results in ferromagnetic interactions between these atoms and gives these elements their ferromagnetic character.

The simulations have been carried out to study and investigate the performance of the photovoltaic J-V characteristics of triple-junction solar cells based on Cu(In,Ga)Se2 absorbers using 2D
Silvaco/Atlas simulator. The triple-junction configuration was considered as a single layer of CGS
on top while the CIGS single layer was separated for middle and bottom cells. The investigations
for CIGS solar cell presented in this article are in close agreement with the already observed
numerical and experimental data. The photovoltaic J-V characteristics for the proposed CGS/
CIGS triple-junction solar cell, such as the short-circuit current density, open-circuit voltage, fill
factor and power conversion efficiency have been investigated and observed to be 13.49 mA/
cm2, 2.64 V, 86.56% and 30.85%, respectively. The proposed configuration offers improved
conversion efficiency up to 33.27% at current matching point. The entire inquiry on CIGS solar
cells yields a prospective idea for single and triple-junction solar cells with high efficiency.

In this study, we presented a novel structure for
a highly sensitive surface plasmon resonance (SPR) sensor, we propose a structure which contains six layers: BK7
prism glass, Gold thin film, Silicon sheets, Gold thin film,
using transition figure of merit (FOM) 16.43 RUI−1metal
dichalcogenides 2D PtSe2 layer and sample medium. We
have been optimizing the thickness of each layer. The highly
performance parameters in this biosensor structure are provided in terms of sensitivity(S), detection accuracy (DA),
quality factor (QF) and figure of merit (FOM). Here, the
addition of the hybrid Silicon—PtSe2 layer between two gold
films increased the sensitivity, but we observed the (DA)
and (QF) is decreased. We find the full at half maximum
also decreased. We investigated the effect of gold thickness.
The maximum sensitivity 200°/RIU and is gained with 35
nm Gold film, 5 nm thickness Silicon and 2 nmPtSe2 layer,
we can be obtained also the configuration with 60 nm Gold
thin film and 3 nm thickness Silicon (6 layer) delivers a
maximum sensitivity (S) of 206°/RIU with figure of merit
(FOM) of 24.03 RUI−1.Our novel structure is optimized for
a highly sensitive surface plasmon resonance (SPR) sensor.

By first-principles calculations with density functional theory and a pseudopotential approach, the structural,
electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc
(N◦60) and P21/c (N◦14) space group are investigated. All computations are determined by a generalized
gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the
GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856
(1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct
band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and
the minimum of the conduction band are both situated at the YA center.

We use an ab-initio approach to analyze the structural, electronic band structure, and thermoelectric properties of
titanium dioxide (TiO2 in rutile phase), and we then use rutile-TiO2 nanoparticles to determine its effects on solgel-produced polyvinyl alcohol/silicon dioxide (PVA/SiO2) hybrid films. The synthesis of hybrid films involved
the incorporation of 1 % rutile-TiO2 nanoparticles in the PVA/SiO2 matrix. The thermoelectric properties of the
resulting hybrid films were characterized by Seebeck coefficient measurements, as well as electrical and thermal
conductivities. The synthesis of PVA/SiO2/Nano-TiO2 films was accomplished with success. The chemical bonds
have amply demonstrated that the PVA backbone is connected to the (SiO2-TiO2) network. TGA testing indicates
that hybrid films are more resistant to higher temperatures than pure PVA films. SiO2 nanoparticles reveal more
effective loading to improve dielectric characteristics compared to TiO2. The best results are obtained in cases of
mechanical, thermal and electrical insulation when both nanofillers are integrated into the polymer matrix. The
findings show that the thermoelectric performance of PVA/SiO2 hybrid films is improved by the addition of (1
%) rutile-TiO2 nanoparticles in the rutile phase. This study provides insights into the potential applications of
rutile-TiO2 nanoparticles in enhancing the thermoelectric properties of hybrid materials and opens up avenues
for further research in this area, and contributes to the growing body of knowledge on enhancing the thermoelectric properties of materials by incorporating rutile-TiO2 nanoparticles into hybrid films synthesized by the
sol-gel method.

The goal of this study is based on the determination of the half-metallic ferromagnetic features of V-doped Cu2O
alloys (Cu2(1-x)V2xO (x = 0, 0.25, 0.50, 0.75 and 1)) using both GGA + U and TB-mBJ-GGA approximations (GGA:
the generalized gradient approximation) within the accurate full potential linearized augmented plane wave plus
local orbitals (FP-LAPW + lo) method implemented in the WIEN2k package. The structural properties are
computed by using the GGA approximation in order to find the equilibrium structural parameters of each alloy,
such as: lattice parameter, bulk modulus and its first-pressure derivative. The electronic properties calculated by
TB-mBJ-GGA and GGA + U approximations show the complete half-metallicity of Cu1.50V0.50O, CuVO,
Cu0.50V1.50O and V2O alloys, in fact, all the half-metallic gaps (EHM) of the compete half-metals are given in this
study. The magnetic properties of the studied alloys show that the majority of the total magnetic moment (MTot)
comes from the V atom with small contributions from Cu atom and the interstitial zone. The N0α and N0β
exchange-splitting constants are given in order to analyze the contributions to conduction and valence bands
during the exchange and splitting process. Furthermore, the hybridization between the 2p-O and 3d-V states (pd hybridization) is the cause for the appearance of feeble magnetic moments on the non-magnetic Cu and O sites
and the reduction of the atomic magnetic moment of the V atom.

Structural, elastic, mechanical and electronic properties of pure and zinc-doped SrTiO3 at the concentration in the range (1–10%) are studied by first-principles calculations. The structural parameters of synthesized compounds agree well with the standard data depicting the growth of stable compounds. A slight obvious increase in the lattice constant of 3.9245Å is observed in Zn-doped SrTiO3 due to the deviation of the atomic radii of Zn and Ti. Elastic constants and mechanical parameters of SrTiO3 are closer to their available theoretical and experimental data. The investigated compounds exhibit brittle behavior for all Zn ratios. The doping zinc concentration reduces the indirect band gap value. The doping concentration 2%, gives a band gap value closer to the experimental one. The band gap of pure SrTiO3 is 1.827eV and after doping with Zn for concentration from 1% to 10%, the optimized values are 1.970, 1.886, 1.802, 1.718, 1.635, 1.552, 1.470, 1.389, 1.310, 1.231 and 1.154eV.

The crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn, Te and Ti) cubic double perovskites are studied within GGA, GGA-mBJ and EV-GGA functionals. The M − Cl bond lengths are shorter and especially in Cs2TiCl6 double perovskite, which reflects the strong interaction between M and Cl atoms and this is correlated with its better chemical stability. The negativity of formation energy and Helmholtz free energy and no imaginary phonon modes throughout the Brillouin zone confirm the thermal, thermodynamic and dynamical stability of these double perovskites. Semiconductors Cs2MCl6 (M = Se, Sn, Te and Ti) double perovskites with flat conduction and valence bands, and an indirect band gap are p-type carriers. A high Seebeck coefficient, adequate ZT values ​​and non-toxicity make these compounds attractive for thermoelectric applications at high temperature and spintronic technology. The empty first conduction band corresponds to their band gap, and the transition occurs from Cl-p to (Se-p, Sn-p, Te-p and Ti-d). The high static dielectric constant and the intense peak of the real part in the ultraviolet energy range favor less the recombination rate of charge carriers and their use in optoelectronic devices. The indirect band gap, high absorption in ultraviolet energy, high static refractive index make these cubic double perovskites as ideal materials for solar cell applications.

The Quaternary Heusler alloys CoFeXAs (X = Cr, Mn and V) fully spin-polarized with half-metallic stability, show
low direct band gap, high absorption in the ultraviolet light, high spin polarization and adequate Seebeck coefficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 μB, 5 μB and 3 μB according
to the Slater-Pauling rule. The obtained minimal energy favors the type I CoFeVAs alloy over the type III
CoFeCrAs and CoFeMnAs alloys. For CoFeCrAs and CoFeMnAs alloys, there is no band gap close to the Fermi
level in the minority-spin, suggesting that they are direct Г–Г band gap semiconductors. Three-dimensional Co,
Fe, and Mn atoms hybridized strongly, with little input from V and As atoms. Co, Fe, Cr, and Mn all have parallel
magnetic moments, which results in ferromagnetic interactions between these atoms and gives these elements
their ferromagnetic character.

The crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn,
Te and Ti) cubic double perovskites are studied within GGA, GGA-mBJ and EV-GGA functionals. The M − Cl
bond lengths are shorter and especially in Cs2TiCl6 double perovskite, which reflects the strong interaction
between M and Cl atoms and this is correlated with its better chemical stability. The negativity of formation
energy and Helmholtz free energy and no imaginary phonon modes throughout the Brillouin zone confirm the
thermal, thermodynamic and dynamical stability of these double perovskites. Semiconductors Cs2MCl6 (M = Se,
Sn, Te and Ti) double perovskites with flat conduction and valence bands, and an indirect band gap are p-type
carriers. A high Seebeck coefficient, adequate ZT values and non-toxicity make these compounds attractive for
thermoelectric applications at high temperature and spintronic technology. The empty first conduction band
corresponds to their band gap, and the transition occurs from Cl-p to (Se-p, Sn-p, Te-p and Ti-d). The high static
dielectric constant and the intense peak of the real part in the ultraviolet energy range favor less the recombination rate of charge carriers and their use in optoelectronic devices. The indirect band gap, high absorption in
ultraviolet energy, high static refractive index make these cubic double perovskites as ideal materials for solar
cell applications.

The main objective of this research is the explanation of the replacement of feldspar limestone
imported from Spain with recycled automotive glass, in order to reduce waste and promote
environmental sustainability. Details and e®orts of making porcelain ceramics from local raw
materials such as quartz, kaolin and glass are also given. Replacing the feldspar with reclaimed
automotive glass shows the e®ect of the Na2O and CaO solvents contained in the glass on the
sintering and crystallization of the studied porcelain. The results showed that the added glass
contributes to the reduction of the density and the acceleration of the sintering process, by
occupying the sites of the open spaces, observed in the samples not containing feldspars.
By reaching a nonporous ratio at a temperature of 1000
C, the melting of the material is
accelerated due to the dissolved oxides it contains, in addition to the linear shrinkage rate in
samples that contain a lot of glass reaching the normal level of porcelain (about 12%) at low
temperature compared to ordinary porcelain.

By first-principles calculations with density functional theory and a pseudopotential approach, the structural, electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc (N°60) and P21/c (N°14) space group are investigated. All computations are determined by a generalized gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856 (1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and the minimum of the conduction band are both situated at the YA center.

By first-principles calculations with density functional theory and a pseudopotential approach, the structural,
electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc
(N◦60) and P21/c (N◦14) space group are investigated. All computations are determined by a generalized
gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the
GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856
(1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct
band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and
the minimum of the conduction band are both situated at the YA center.

Ab-initio simulations based on density functional theory as contained in the WIEN2k code using GGA, GGA+U, and mBJ approximations were used to perform the calculations. The energy of cohesion is minimal for FeMnCrSb, indicating that it is the most stable structure, with a lattice constant of 5.95 Å and 6.2184 Å for GGA and GGA+U. The ferromagnetic state is less stable than ferrimagnetic states in all studied quaternary Heusler. All the band structures are metallic, with the exception of the spin up case using GGA+U and mBJ approaches, where the semiconducting character is predicted. The amount of absorption and band gap validates the candidature of CoFeCrAl, CoFeMnSi, CoMnCrSi, and FeMnCrSb as absorber materials for photovoltaic devices. The high values of 0.8, 0.9, 0.95 and 1 for figure of merit (ZT) at 300 K were obtained for CoFeMnSi, CoFeCrAl, CoMnCrSi, and FeMnCrSb allowing their use in spintronic and thermoelectric applications. The resistivity of studied quaternary alloys is little sensitive to the temperature, while the electronic conductivity and power factor are proportional to the temperature

The crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn,
Te and Ti) cubic double perovskites are studied within GGA, GGA-mBJ and EV-GGA functionals. The M − Cl
bond lengths are shorter and especially in Cs2TiCl6 double perovskite, which reflects the strong interaction
between M and Cl atoms and this is correlated with its better chemical stability. The negativity of formation
energy and Helmholtz free energy and no imaginary phonon modes throughout the Brillouin zone confirm the
thermal, thermodynamic and dynamical stability of these double perovskites. Semiconductors Cs2MCl6 (M = Se,
Sn, Te and Ti) double perovskites with flat conduction and valence bands, and an indirect band gap are p-type
carriers. A high Seebeck coefficient, adequate ZT values and non-toxicity make these compounds attractive for
thermoelectric applications at high temperature and spintronic technology. The empty first conduction band
corresponds to their band gap, and the transition occurs from Cl-p to (Se-p, Sn-p, Te-p and Ti-d). The high static
dielectric constant and the intense peak of the real part in the ultraviolet energy range favor less the recombination rate of charge carriers and their use in optoelectronic devices. The indirect band gap, high absorption in
ultraviolet energy, high static refractive index make these cubic double perovskites as ideal materials for solar
cell application

In the pursuit of sustainable porcelain production, this research examines the potential of using
recovered automotive glass as a substitute for traditional feldspar, specifically feldspar imported
from Spain. Porcelain samples were sintered at different temperatures and with varied proportions
of automotive glass. The crystalline phases formed post-sintering were determined
through X-ray diffraction and quantified by dissolving the porcelain in concentrated hydrofluoric
acid. Results revealed that the inclusion of automotive glass, owing to its dissolved oxide content,
accelerated the porcelain melting process and led to an increase in the vitreous phase. Notably,
anorthite phases became dominant and mullite formation was evident at 1100 ◦C, stabilizing in
samples G00 and G10, and then increasing at 1200 ◦C due to the emergence of secondary mullite.
This secondary mullite forms from the residual silica after the primary mullite formation and the
aluminium in the feldspars, which is about 17 %. For samples G20 and G30, only primary mullite
was observed due to the decreased aluminium content resultant from feldspar replacement by
glass. These findings underscore the viability of automotive glass in porcelain production,
providing a sustainable and effective alternative to feldspar

The Quaternary Heusler alloys CoFeXAs (X = Cr, Mn and V) fully spin-polarized with half-metallic stability, show
low direct band gap, high absorption in the ultraviolet light, high spin polarization and adequate Seebeck coefficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 μB, 5 μB and 3 μB according
to the Slater-Pauling rule. The obtained minimal energy favors the type I CoFeVAs alloy over the type III
CoFeCrAs and CoFeMnAs alloys. For CoFeCrAs and CoFeMnAs alloys, there is no band gap close to the Fermi
level in the minority-spin, suggesting that they are direct Г–Г band gap semiconductors. Three-dimensional Co,
Fe, and Mn atoms hybridized strongly, with little input from V and As atoms. Co, Fe, Cr, and Mn all have parallel
magnetic moments, which results in ferromagnetic interactions between these atoms and gives these elements
their ferromagnetic character.

Zinc monochalcogenides, specifically ZnS serve as exemplary representatives of II-VI semiconductors and have the ability to adopt either zinc-blende (ZnX-z) or wurtzite (ZnX-w) crystal structures. Notably, ZnX-z phases exhibit optical isotropy, while ZnX-w phases display anisotropy, with the c-axis serving as the polar axis. ZnS featuring a wide direct band gap of approximately 3.37 eV at room temperature, emerges as a quintessential semiconductor employed extensively in optoelectronic applications. Furthermore, ZnS exhibits transparency within the visible light spectrum and possesses the added advantage of environmental friendliness, attributed to the abundant presence of zinc in the Earth's crust. Among the family of IIB-VIA compounds, namely ZnS, this material crystallizes in the cubic zinc-blende structure under ambient pressure, boasting direct energy band gaps. Notably, these wide band-gap semiconductors are of paramount interest due to their capability to emit light even at room temperature. Utilizing computational tools such as CASTEP offers a robust means for designing and enhancing these materials, facilitating the development of advanced optoelectronic devices. In this study, we delved into the electronic structure and optical characteristics of ZnS systems, employing first principles through the ultra-smooth pseudopotential approach of density functional theory and the generalized gradient approximation method implemented with CASTEP. Our investigation yielded the following findings: The network parameters exhibited varying values, making it feasible to deposit these materials on different substrates. The binary alloy holds particular interest due to its wide bandgap 2.698 eV for ZnS. The results obtained for the structural, physical, and optical properties closely align with existing theoretical and experimental data, affirming the accuracy of our calculation methodology. The properties of pure ZnS materials suggest significant potential for use in solar cells.

The structural, electronic, optical and thermodynamic properties of SrxCa1-xO, BaxSr1-xO and BaxCa1-xO ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for SrxCa1-xO and BaxSr1-xO exhibits a marginal deviation from the Vegard’s law, while the BaxCa1-xO lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time.

The purpose of this research is to investigate the structural, electronic, and optical properties of ZnX compounds, particularly those with
X = Te, S, and O, which have direct bandgaps that make them optically active. To gain a better understanding of these compounds and
their related properties, we conducted detailed calculations using density functional theory (DFT) and the CASTEP program, which uses
the generalized gradient approximation (GGA) to estimate the cross-correlation function. Our results for lattice modulus, energy bandgap,
and optical parameters are consistent with both experimental data and theoretical predictions. The energy bandgap for all compounds is
relatively large due to an increase in s-states in the valence band. Our findings suggest that the optical transition between (O - S - Te) - p
states in the highest valence band and (Zn - S - O) - s states in the lowest conduction band is shifted to the lower energy band. Therefore,
ZnX compounds (X = Te, S and O) are a promising option for optoelectronic device applications, such as solar cell materials

Cet ouvrage qui comprend des exercices corrigés a été réalisé dans le but de faciliter la compréhension de la structure de la matière et les liaisons chimiques. Ce document est destiné principalement aux étudiants de la première année des filières Sciences de la Matière (SM), Sciences Techniques (ST), et Sciences de la Nature et de la Vie (SVI). Cette édition d'exercices corrigés permet aux étudiants de ces filières d’acquérir une méthodologie adéquate pour résoudre les problèmes de la chimie de l’atome.
Ce manuscrit se compose de cinq parties, où on étudie principalement la structure de l'atome, les modèles quantique et ondulatoire de l'atome de Bohr, la classification périodique et la structure électronique des éléments ainsi que leurs propriétés et enfin les liaisons chimiques entre atomes et molécules.
Chaque chapitre comprend une série d’exercices choisie pour son intérêt et sa diversité. On reporte aussi le corrigé détaillé de cette série afin que les étudiants puissent assimiler le cours de cette matière.
On propose dans le premier chapitre des exercices de connaissances générales sur la structure de l’atome, sur les isotopes et les défauts de masse.
Le second chapitre est consacré au calcul des différents paramètres de l’atome d’hydrogène et des ions hydrogénites selon le modèle de Bohr. L'étude des différentes séries spectrales de l’atome d’hydrogène est également bien détaillée.
Dans le troisième chapitre, on traite le modèle ondulatoire de l’atome qui comprend la relation de Louis De Broglie, l'équation de Schrödinger, les fonctions d’ondes et les orbitales atomiques. On détermine aussi les structures électroniques des éléments en utilisant les règles de remplissage des électrons dans les différentes couches et sous-couches de l’atome.
Les exercices que contient le chapitre quatre servent à déterminer la structure électronique d’un atome et son numéro atomique suivant son classement dans le tableau périodique. Ces exercices permettent aussi de trouver le groupe ou la période auxquels appartient l’atome.
Le dernier chapitre traite des exercices d'application sur les différentes liaisons chimiques possibles entre les atomes et molécules.
Mon souhait est que ce modeste travail améliore l'encadrement et la formation dans notre Université et qu'il sera d'une grande importance à nos étudiants pour acquérir une base solide en chimie de la matière.

Ab-initio simulations based on density functional theory as contained in the WIEN2k code using
GGA, GGA+U, and mBJ approximations were used to perform the calculations. The energy of
cohesion is minimal for FeMnCrSb, indicating that it is the most stable structure, with a lattice
constant of 5.95 Å and 6.2184 Å for GGA and GGA+U. The ferromagnetic state is less stable than
ferrimagnetic states in all studied quaternary Heusler. All the band structures are metallic, with
the exception of the spin up case using GGA+U and mBJ approaches, where the semiconducting
character is predicted. The amount of absorption and band gap validates the candidature of
CoFeCrAl, CoFeMnSi, CoMnCrSi, and FeMnCrSb as absorber materials for photovoltaic devices.
The high values of 0.8, 0.9, 0.95 and 1 for figure of merit (ZT) at 300 K were obtained for
CoFeMnSi, CoFeCrAl, CoMnCrSi, and FeMnCrSb allowing their use in spintronic and thermoelectric
applications. The resistivity of studied quaternary alloys is little sensitive to the temperature,
while the electronic conductivity and power factor are proportional to the temperature.

We derived the chemical compositions and the micro hardness of the two studied steels Fe20Mn5Cr and Fe9S28Mn. The contamination of these two compounds by oxygen gives the series M2O3 (M = Fe, Cr, Al). Rhombohedral crystal structure of these compounds was determined by means of the X-rays diffraction. First principles calculations were performed to investigate structural, elastic and mechanical properties of M2O3 (M = Fe, Cr, Al) compounds at equilibrium pressure. Fe2O3 and Cr2O3 are classified as ductile materials, while Al2O3 is brittle. The Debye temperature, the elastic wave velocities and the integration of elastic wave velocities in various directions of the single crystal were obtained. All these compounds are elastically and chemically stable. The calculated elastic constants are in good agreement with the experiment values in the approximation of the gradient generalized for the correlation and exchange potential. We calculated the partial and total densities of states PDOD and TDOS for M2O3 (M = Fe, Cr, Al) compounds. As a result, electronic bands, DOS at the Fermi level, were obtained for the first time especially for Fe2O3 and Cr2O3.

We studied the ternary acetylides A2MC2 (A = Na, K) and (M = Pb, Pt) with trigonal structures by using the density functional theory (DFT) as implemented in the CASTEP code. The calculated lattice parameters and atomic fractional coordinates were in agreement with previous calculations and experimental data. A set of isotropic elastic parameters and related properties, namely the module and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature were numerically estimated in the frame work of the Voigt-Reuss-Hill approximation. The absorption, energy-loss and dielectric function were calculated. We studied the main contribution to the optical spectra from the transition from the top four valence bands towards the lower three first one of conduction based on the electronic structures.

Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical characteristics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x  = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of have an indirect band gap, while manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature.

Ce polycopié est destiné aux étudiants de première année du système Licence-Master-Doctorat (L.M.D), spécialité : Sciences et Technologie (S.T) Il comporte un rappel de cours et des exercices résolus sur les différents chapitres du module chimie 2 (thermodynamique). Le cours permet d’acquérir certaines notions fondamentales en thermodynamique facilitant ainsi une meilleure maitrise des concepts fondamentaux appliqués dans le domaine d’ingénierie thermique. Le polycopié est réparti en cinque chapitres : Le premier chapitre: Généralités sur la thermodynamique avec un rappel de notions mathématiques ainsi que quelques définitions en rapport avec la thermodynamique en général. Le deuxième chapitre : Température, Chaleur, travail et Calorimétrie Le troisième chapitre : Enoncé du premier principe de la thermodynamique. Le quatrième chapitre : Applications du premier principe en thermochimie et le cinquième chapitre : Second principe de la thermodynamique.

In this paper, we present a detailed theoretical investigation on the structural, elastic, electronic and optical properties of the perovskite oxides SrThO3 and SrZrO3 by using the pseudo-potential plane wave (PP-PW) method. The computed lattice constants of SrXO3 (X = Th and Zr) are in excellent agreement with the available experimental data. SrThO3 and SrZrO3 are direct (Γ–Γ) and indirect (Γ–R) band gap semiconductors, respectively. Under pressure effect a crossover between the indirect band gap (R–Γ) and the direct band gap (Γ–Γ) curves occurs at about 35 GPa for SrZrO3, resulting in the energy minimum of direct gap (Γ–Γ) for this compound. The covalence in the Zr–O and Th–O bonds arises due to the hybridization between O–p and Zr–d (Th–d) states. Under pressure effect, the threshold energy becomes slightly greater (smaller) for SrZrO3 (SrTO3) for 3.21 (2.28) eV and the main peaks are shifted towards higher energies. Although the positions of all peaks shifted under pressure, they still have the same type as those at zero pressure, with decreasing the intensity of the main peaks.

This study investigated the effect of aging on the precipitation and kinetics of second phase Mg17Al12 in AZ91 magnesium alloy (Mg-9 wt% Al-1 wt% Zn), using X-ray diffraction, microhardness measurements and differential scanning calorimetric analysis (DSC). With the last instrument, the all samples were heated from room temperature to 400 °C, at heating rates of 10–30 °C/min. The results were supplemented by measuring the average of activation energies, using isothermal treatments by Johnson–Mehl–Avrami (JMA) methods and by non-isothermal treatments using Ozawa, Boswell, Kissinger, Mahadevan, Augis and Bennett methods, were around 67.18 and 62.02 kJ/mol. The frequency factor k0 calculated by the isothermal treatment is equal to 1.24 109 s−1. In non-isothermal treatment, the numerical factor m and the Avrami parameter n is estimated to be approximately equal to 3 and 2.79 respectively. This value corresponding that the bulk nucleation with a constant number of nuclei was dominant in three-dimensional (polyhedron) controlled by interface reaction.

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

The lead free halides double perovskites show a particular interest in the conception of perovskites solar cells. We predicted the lattice constant and the atomic Wycko position of these lead free halide double perovskites Cs2AgBiX6 (X = Br, Cl) under pressure effect. The alloying ability of crystal, elastic constants and related parameters, electronic and optical properties have been studied using pseudo potential plane wave method based on the density functional theory. The investigated lead free halide double perovskites Cs2AgBiX6 (X = Br, Cl) show a weaker resistance to compression along the a-axis. This result also proves the existence of a directional bonding between atoms and a weaker resistance to compression along the a-axis The band structure indicates that Cs2AgBiX(X = Br, Cl) are X–L indirect gap semiconductors. Our computed bulk modulus and its pressure derivative of double perovskites Cs2AgBiX6 (X = Br, Cl) are predictions. The calculated elastic constants of Cs2AgBiX6 (X = Br, Cl) at equilibrium and under pressure effect are predictions.

Using ab initio spin-polarized density functional theory calculations, the structural, elastic and thermodynamic properties of the orthorhombic and hexagonal phases of the iron carbide Fe7C3 were investigated. The calculated ground-state lattice parameters are in good agreement with the available corresponding theoretical and experimental data. The single-crystal and polycrystalline aggregate elastic constants, sound velocities, Debye temperature, brittle/ductile character and elastic anisotropy have been estimated. The calculated bulk modulus values of both considered phases are very close and are approximately equal to 262 GPa, which classifies the title compounds among the hard materials. The temperature and pressure dependencies of the unit-cell volume, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity, and Debye temperature were investigated using the quasi-harmonic Debye model.

We studied the profiles of the micro hardness in the nuances 9SMn28, 42CrMo4 and CK45, which have a rapid decline to the depth 0.1 mm, and then slowly decrease to the value of the characteristic of the casting material. The surface layer contains mostly the iron nitrides phases FeyN (y = 1, 2, 3, 4). We use first principles to study the electronic and magnetic properties of some structural phases. We calculated the lattice parameters of all the compounds; our results show good agreement with other calculations. The estimated formation energies first show a decrease then an increase with the nitrogen content. The contribution of the PDOS is due to the Fe-3d and N-2p states in Fe(1–4)N. We used experimental and theoretical studies to determine all of the phases existing in a nitride layer.

The structural, elastic, electronic and magnetic properties of the diluted magnetic semiconductors MnxCa1−xS in the rock-salt phase have been investigated using first-principles calculations with both LDA and LDA + U functional. Features such as lattice constant, bulk modulus, elastic constants, spin-polarized band structure, total and local densities of states have been computed. We predict the values of the exchange constants and the band edge spin splitting of the valence and conduction bands. The hybridization between S-3p and Mn-3d produces small local magnetic moment on the nonmagnetic Ca and S sites. The ferromagnetism is induced due to the exchange splitting of S-3p and Mn-3d hybridized bands. The total magnetic moment per Mn of MnxCa1−xS is 4.4μB and 4.5μB for LDA and LDA + U functional and is independent of the Mn concentration. The unfilled Mn-3d levels reduce the local magnetic moment of Mn from its free space charge value of 5μB–4.4μB and4.5μB for LDA and LDA + U functional due to 3p–3d hybridization.

Electronic band structure and lattice dynamical properties of CaxMg1−xS alloys in the rock-salt phase have been investigated. The calculations are performed in the framework of ab initio pseudo-potential approach within the generalized gradient approximation. Reasonable agreement is generally obtained between our results and the available experimental observations and previous calculations. The deviation of the alloy lattice constant and bulk modulus from linearity has been examined and discussed. Fundamental band gaps and Г–X and Г–L separations in higher-lying conduction bands are predicted. In agreement with reflectivity spectrum and recent optical absorption spectrum measurements, CaS in the rock-salt phase is found to be an indirect band-gap (Г–X). Similarly to CaS, the electronic band structure calculations showed that MgS is also an indirect band-gap (Г–X) semiconductor. However, a system transition between indirect and direct structures has been predicted in the Ca concentration range 0.12–0.83. Upon alloying the phonon modes are significantly changed showing that the longitudinal optical–transverse optical (LO–TO) splitting becomes narrower as one proceeds from pure rock-salt MgS to pure rock-salt CaS.

The structural, elastic, electronic and optical properties of the gallium monohydrides BaGaXH (X=Si, Ge, Sn) have been investigated by means of first principles calculations. The low values of the B/G ratio of these compounds correspond to the brittle nature, which is due to the hydrogen presence. The bulk modulus, Young's modulus, shear modulus decrease from Si to Sn for BaGaXH (X=Si, Ge, Sn) in the same column in the periodic table. Also the Debye temperature of these compounds has a relative high value indicating that they possess good thermal conductivity. The mean sound velocities have a progressive decrease from silicon (Si) to tin (Sn).

The alkaline platinum hydrides are considered the most promising as hydrogen storage materials. The alloying ability of crystal, elastic constants and related parameters, electronic and optical properties have been studied using pseudo-potential plane–wave method based on the density functional theory. The investigated compounds show a weaker resistance to compression along the principal a-axis and their resistance to shear deformation is lower than the resistance to the unidirectional compression. The band structure indicates that A2PtH6 (A=K, Rb and Cs) are X–X direct gap semiconductors. The effective electron mass at equilibrium has been predicted towards X–Γ, X–W and L–W directions. The strong hybridization between Pt-d and H-s states in the upper valence band translates the existence of covalent bonding character in these compounds. The static optical dielectric constant is inverse proportional to the fundamental gap.

We report a detailed study of the compositional dependence of the structural, elastic, electronic and dynamical properties of the quaternary alloys matched to AlP using pseudo-potential plane-wave method based on the density functional theory. The reliability and accuracy of the predicted physical properties mentioned above for are tested by comparing the calculated lattice constant, elastic constants and phonon dispersion curves for the binary AlP with the available experimental and theoretical data in the literature.

Structural, electronic and optical properties of the ZnSc2S4 and CdSc2S4 cubic spinels have been investigated by means of the full-potential (linearized) augmented plane wave plus local orbitals based on density functional theory. The exchange-correlation potential is treated by the GGA–PBEsol [J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett. 100 (2008) 136406] and the recently proposed modified Becke–Johnson potential approximation (mBJ) [F. Tran, P. Blaha, Phys. Rev. Lett. 102 (2009) 226401], which successfully corrects the band-gap problem found with GGA for a wide range of materials. The obtained structural parameters are in good agreement with the available experimental data. This gives support for the predict properties for ZnSc2S4 and CdSc2S4. The band structures reveal that both compounds are semiconductor with a direct gap. The obtained gap values show that mBJ is superior for estimating band gap energy. We have calculated the electron and hole effective masses in different directions. The density of states has been analyzed. Based on our electronic structure obtained using the mBJ method we have calculated various optical properties, including the complex dielectric function ɛ(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω) and electron energy-loss function L(ω) as functions of the photon energy. We find that the values of zero-frequency limit ɛ1(0) increase with decreasing the energy band gap in agreement with the Penn model. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures.

We present results of ab initio calculations concerning lattice dynamical and thermal properties of MgS, CaS and their ternary mixed crystals CaxMg1−xS in zinc-blende structure. Results for the phonon modes, dielectric constants, Fröhlich coupling parameter, polaron effective mass, entropy and heat capacities are given for CaxMg1−xS within a composition range 0–1. Generally good agreement is obtained between our results and data available in the literature. Other case, our results are predictions.

We employed the density-functional perturbation theory (DFPT) within the generalized gradient approximation (GGA), the local density approximation (LDA) and the virtual-crystal approximation (VCA) to study the effect of composition on the structure, stability, energy gaps, electron effective mass, the dynamic effective charge, optical and acoustical phonon frequencies and static and high dielectric constants of the rock-salt CaxMg1−xSe and CaxMg1−xTe alloys. The computed equilibrium lattice constant and bulk modulus show an important deviation from the linear concentration. From the Voigt–Reuss–Hill approximation, CaxMg1−xSe and CaxMg1−xTe present lower stiffness and lateral expansion. For Ca content ranging between 0.25 and 0.75, the elastic constants, energy gaps, electron effective mass and dynamic effective charge are predictions. The elastic constants and computed phonon dispersion curves indicate that these alloys are mechanically stable.

M3X (M=Cr, V; X=Si, Ge) compounds are studied using first-principles calculations based on the Density Functional Theory (DFT). It is found that the bulk of Cr3X (X=Si, Ge) compounds are comparable to those of Al2O3, the nearest-neighbor distance DM−M and DM−X in these compounds increase and the bulk modulus decrease, there is a strong interaction between M and M (M=Cr the interaction is stronger). Also the interaction between M (M=Cr, V) and X (X=Ge) is negative, an anti-bonding-type interaction is dominant between these atoms.

Based on the density functional theory as implemented in the Abinit code under the virtual crystal approximation, the lattice constant, bulk modulus, elastic constants, gap energies, electron effective mass, the dielectric constants and born effective charge in In1−x−yAlxGayAs have been calculated with both GGA and LDA in the range 0≤y≤0.9801. The optical and acoustical phonon frequencies, Fröhlich coupling parameter, deformation energy and polaron effective mass are calculated and their dependence on the Ga content is examined. For AlAs, our results are in reasonable agreement with the known data in the literature; while for other contents our treatments are predictions.

The structural, elastic, electronic, optical and thermodynamic properties of the cubic perovskite-type hydride KMgH3 have been investigated using pseudo-potential plane-wave method based on the density functional theory. Computed equilibrium lattice constant agrees well with the available experimental and theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A linear pressure dependence of the elastic stiffnesses is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation for KMgH3 polycrystalline aggregate. The analysis of the site-projected l-decomposed density of states and charge density shows that the bonding is predominantly of ionic nature. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature effect on the lattice constant, bulk modulus, heat capacity and Debye temperature is calculated.

Structural, elastic, electronic and thermal properties of the MAX phase Nb2SiC are studied by means of a pseudo-potential plane-wave method based on the density functional theory. The optimized zero pressure geometrical parameters are in good agreement with the available theoretical data. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contractions along the -axis were higher than those along the -axis. The elastic constants and elastic wave velocities are calculated for monocrystal Nb2SiC. Numerical estimations of the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature for ideal polycrystalline Nb2SiC aggregates are performed in the framework of the Voigt–Reuss–Hill approximation. The band structure shows that Nb2SiC is an electrical conductor. The analysis of the atomic site projected densities and the charge density distribution shows that the bonding is of covalent–ionic nature with the presence of metallic character. The density of states at Fermi level is dictated by the niobium d states; Si element has a little effect. Thermal effects on some macroscopic properties of Nb2SiC are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variations of the primitive cell volume, volume expansion coefficient, bulk modulus, heat capacity and Debye temperature with pressure and temperature in the ranges of 0–40 GPa and 0–2000 K are obtained successfully.

The isothermal and non-isothermal ageing of an Al-2.4 wt% Cu alloy have been studied using X-ray diffraction analysis and differential scanning calorimetry (DSC) at different heating rates. Quantitative metallography methods have been applied to measure the corresponding transformed volume fractions at various temperatures and times of precipitation. The variation of the heating rate using DSC technique has allowed us to calculate two kinetics parameters of precipitation which are the Avrami exponent and the activation energy of the process using Kissinger, Ozawa and Bosswell methods. These parameters are similar to those found for the precipitation reaction of θ′ and θ (Al2Cu) phases.

The structural, elastic, electronic, optical and thermal properties of α phase in LiBeN semiconductor have been studied using pseudo-potential plane wave method based on the density functional theory. The computed lattice parameter agrees well with previous theoretical work. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation for α-LiBeN polycrystalline aggregate. The assignments of the structures in the optical spectra and band structure transitions have been examined and discussed. The thermal effect on heat capacities is investigated by the quasi-harmonic Debye model. To the best of our knowledge, most of the studied properties of the material of interest are reported for the first time.

The structural, electronic, optical and thermodynamic properties of SrxCa1−xO, BaxSr1−xO and BaxCa1−xO ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for SrxCa1−xO and BaxSr1−xO exhibits a marginal deviation from the Vegard's law, while the BaxCa1−xO lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time.

Various physical properties of the cubic perovskite-type oxide BiScO3 have been investigated using the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT). The computed equilibrium lattice parameters agree well with the available theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for BiScO3 polycrystalline aggregate. The analysis of the site-projected -decomposed density of states, charge transfer and charge density shows that bonding is predominantly of ionic nature. We distinguish hybridization between Sc-d states and - states in the valence bonding region. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermal effect on the lattice constant, bulk modulus, heat capacities and thermal expansion coefficient is calculated.

A computed investigation on the structural, elastic, electronic, phonon frequencies and thermal properties of AlxScyB1−x−yN quaternary alloys in the zinc-blend phase has been made with first-principles methods. The information on the lattice constant, lattice matching to AlN substrate and energy band gaps is indispensable for various practical applications. We have studied the effect of Sc concentration y (y = 0, 0.152, 0.303, 0.455 and 0.607) on the lattice constant, bulk modulus, elastic constants C11, C12 and C44, band gaps, optical phonon frequencies (ωTO and ωLO), static and high-frequency dielectric coefficient ɛ(0) and ɛ(∞) and dynamic effective charge Z*. We remark an important deviation from the linear concentration dependence of the lattice constant and bulk modulus. The shear moduli, Young's modulus, Poisson's ratio were estimated in the frame work of the Voigt–Reuss–Hill approximation. The resistance to changes in bond length and lateral expansion in AlxScyB1−x−yN increase with increasing y concentration. We observe that at y concentration about 0.11, the Г–X indirect fundamental gap becomes Г–Γ direct fundamental gap in AlxScyB1−x−yN. There is well agreement between our results and the experiment data for AlN binary compound which is a support for those of the quaternary alloys that we report for the first time.

Density functional theory pseudo-potential plane-wave calculations are performed in order to predict the structural, elastic and thermodynamic properties of the newly discovered tetragonal intermetallic SrPd2Ge2. The computed equilibrium lattice constants and the internal parameter are in good agreement with the experimental findings. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contraction along the axis is higher than along the axis. The single-crystal elastic constants and related properties are calculated using the static finite strain technique. We predicted the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio for ideal polycrystalline SrPd2Ge2 aggregates, using the Voigt–Reuss–Hill approximations. We estimated the Debye temperature and minimum thermal conductivity of SrPd2Ge2 from the average sound velocity. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the primitive cell volume, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature are investigated. This is the first quantitative theoretical prediction of the elastic and thermodynamic properties of the SrPd2Ge2 compound, and it still awaits experimental confirmation.

The structural, elastic, electronic and thermal properties of the MAX phases Ti2SiC and Cr2SiC are studied by means of the pseudo-potential plane wave method within GGA and LDA. The effect of pressure on the normalized lattice constants a/a0 and c/c0 and the internal parameter z is investigated. Our results of elastic constants, sound velocities and Debye temperature are predictions. The Ti2SiC and Cr2SiC compounds behave as ductile material and show a stronger anisotropy. The analysis of the band structure and density of states show that these compounds are electrical conductors, having a strong directional bonding between Ti and C and Cr and C atoms assured by the hybridization of Ti–d and Cr–d atom states with C–p atom states. The thermal effect on the primitive cell volume, bulk modulus, heat capacities CV and CP were predicted using the quasi-harmonic Debye model.

A theoretical study on the structural, elastic, electronic and lattice dynamic properties of AlxYyB1−x−yN quaternary alloys in zinc-blend phase has been carried out with first-principles methods. Information on the lattice parameter, the lattice matching to available substrates and energy band-gaps is a prerequisite for many practical applications. The dependence of the lattice parameter a, bulk modulus B, elastic constants C11, C12 and C44, band-gaps, optical phonon frequencies (ωTO and ωLO), the static and high-frequency dielectric coefficients ε (0) and ε (∞) and the dynamic effective charge Z⁎ were analyzed for y=0, 0.121, 0.241, 0.362 and 0.483. A significant deviation of the bulk modulus from linear concentration dependence was observed. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation. The resistance to changes in bond length and lateral expansion in AlxYyB1−x−yN increase with increasing y concentration. We observe that at y concentration about 0.035 and 0.063, AlxYyB1−x−yN changes from brittle to ductile and Γ–X indirect fundamental gap becomes Γ–Γ direct fundamental gap. There is good agreement between our results and the available experimental data for the binary compound AlN, which is a support for those of the quaternary alloys that we report for the first time.

The structural, elastic, electronic, optical and thermal properties of the semiconductor perovskite CsPbCl3 were investigated using the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA) and local density approximation (LDA). The computed lattice constant agrees reasonably with experimental and theoretical ones. The CsPbCl3 crystal behaves as ductile material. The valence bands are separated from the conduction bands by a direct band gap R–R. We distinguished hybridization between Pb-p states and Cl-p states in the valence bonding region. Under compression at P=30 GPa, this material will have a metallic character. The thermal effect on the lattice constant, bulk modulus, Debye temperature and heat capacity CV was predicted using the quasi-harmonic Debye model. To the author's knowledge, most of the studied properties are reported for the first time.

Information on the energy band gaps, the lattice parameters and the lattice matching to available substrates is a prerequisite for many practical applications. A pseudopotential plane-wave method as implemented in the ABINIT code is used to the AsxPyN1−x−yB quaternary alloys lattice matched to BP substrate to predict their energy band gaps and lattice dynamic properties. The range of compositions for which the alloy is lattice matched to BP is determined. Very good agreement is obtained between the calculated values and the available experimental data. The compositional dependence of direct and indirect band gaps has been investigated. We study the variation of elastic constants, the optical phonon frequencies (ωTO and ωLO), the high-frequency dielectric coefficient ε(∞) and the born effective charge Z∗ with P concentration.

The stability, structural parameters, elastic constants, electronic and optical properties of perovskites CsCaH3 and RbCaH3 were investigated by the density functional theory. The calculated lattice parameters are in agreement with previous calculation and experimental data. The energy band structures, density of states, born-effective-charge and Mulliken charge population were obtained. The perovskites CsCaH3 and RbCaH3 present a direct band gap of 3.15 eV and 3.27 eV at equilibrium. The top of the valence bands reflects the s electronic character for both structures. Furthermore, the absorption spectrum, refractive index, extinction coefficient, reflectivity, energy-loss spectrum, and dielectric function were calculated. The origin of the spectral peaks was interpreted based on the electronic structures. The static dielectric constant and refractive index are indeed, inverse proportional to the direct band gap.

The structural, elastic, electronic, optical and thermodynamic properties of the perovskite chloride CsCdCl3 were investigated using the pseudo-potential plane wave (PP-PW) within the Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA). The computed lattice parameter agrees well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal rigidity and mechanical stability have been discussed. Energy band structure shows that the investigated material is indirect energy band gap semiconductor. The static dielectric constant and static refractive index are indeed, proportional to the fundamental indirect band gap. The thermal effect on the lattice parameter, bulk modulus, volume expansion coefficient, Grüneisen parameter, heat capacities and Debye temperature were predicted using the quasi-harmonic Debye model. To the best of the authors’ knowledge, most of the studied properties are reported for the first time.

Information on the energy band gaps, the lattice parameters and the lattice matching to available substrates is a prerequisite for many practical applications. A pseudopotential plane-wave method as implemented in the ABINIT code is used to the AsxPyN1−x−yAl quaternary alloys lattice matched to AlP substrate to predict their energy band gaps and optical properties. The range of compositions for which the alloy is lattice-matched to AlP is determined. Very good agreement is obtained between the calculated values and the available experimental data. The Debye temperature increase when the bulk modulus is enhanced. We study the variation of elastic constants, the optical phonon frequencies (ωTO and ωLO), the static and high-frequency dielectric coefficient ɛ(0) and ɛ(∞) and the dynamic effective charge Z* with P concentration (y).

The structural, elastic, electronic and optical properties of XO (X= Ca, Sr and Ba) compounds were investigated by the density functional theory. A good agreement was found between our calculated results and the available theoretical and experimental data of the lattice constants. Young's modulus, Poisson ratio, bulk modulus, elastic constants and their pressure derivatives are also calculated. SrO and BaO compounds present a transition phase at 39.72 and 27.28 GPa. The SrO compound shows a change from direct band gap (Γ–Γ) to indirect band gap (Γ–X) at about 15 GPa. The top of the valence bands reflects the s electronic character for all structures. We investigate the effective mass of electrons as function of pressure at the Γ point for CaO, SrO and BaO compounds. Calculations of the optical spectra have been performed for the energy range 0–60 eV. The origin of the spectral peaks was interpreted based on the electronic structures. The enhancement of pressure increases the static dielectric function and refractive index of CaO, SrO and BaO.

We present structural, elastic, electronic and optical properties of the perovskites SrMO3 (M=Ti, and Sn) for different pressure. The computational method is based on the pseudo-potential plane wave method (PP-PW). The exchange-correlation energy is described in the generalized gradient approximation (GGA). The calculated equilibrium lattice parameters are in reasonable agreement with the available experimental data. This work shows that the perovskites SrTiO3, and SrSnO3 are mechanically stable and present an indirect band gaps at the Fermi level. Applied pressure does not change the shape of the total valence electronic charge density and most of the electronic charge density is shifted toward O atom. Furthermore, in order to understand the optical properties of SrMO3, the dielectric function, absorption coefficient, optical reflectivity, refractive index, extinction coefficient and electron energy-loss are calculated for radiation up to 80 eV. The enhancement of pressure decreases the dielectric function and refractive indices of SrTiO3 and SrSnO3.