M. KETFI Mohammed elamin

In this study, the optoelectronic, structural, thermal and thermoelectric properties of CsLaO2, HgMgO2, KInO2, and RbInO2 were investigated based on density functional theory incorporated in the Wien2K code, the semi-classical Boltzmann approximation integrated in the BoltzTraP program, and the quasi-harmonic Debye model implemented in the Gibbs2 program. The four compounds exhibit semiconductor character with indirect band gaps: 3.97 eV (C-A) for KInO2, 4 eV (C-H) for RbInO2, 2.82 eV (M-L) and CsLaO2 and 0.3 eV (C-A) for HgMgO2. The effect of temperature on the heat capacity, thermal expansion coefficient, and entropy and lattice thermal conductivity was also studied. Furthermore, the optical properties of the studied compounds, including reflection and refractive coefficients, optical conductivity, and the optical absorption coefficient, were investigated to ascertain their suitability for use in photovoltaic applications. Furthermore, this study investigated the dependence of the thermoelectric parameters, including the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and factor of merit, on temperature and electron/hole concentration.

In this investigation, the structural, electronic, optical, and thermoelectric qualities of Sr2P7Br, a double Zintl salt with a heptaphosphanortricyclane configuration, were assessed using the first-principles FP-LAPW approach. The exchange-correlation interactions were simulated using the GGA-PBEsol method to analyze the structural properties, whereas the TB-mBJ functional was utilized to assess the electronic, optical, and thermoelectric features. The Birch–Murnaghan equation of state was used to fit the total energy versus unit cell volume in order to determine the relaxed lattice parameter, bulk modulus, and its pressure derivative. The calculated equilibrium structural parameters and bulk modulus agree with the corresponding experimental and theoretical values. Based on the results of the computed density of states and band structure, Sr2P7Br is classed as a wide bandgap semiconductor with an indirect bandgap (R-M) of 4.14 eV. The QTAIM descriptors computed at critical points forecast the covalent and ionic characteristics of the bonds between the compound's atoms. The optical coefficients, comprising the complex dielectric function, reflectivity, complex refractive index, absorption coefficient, and electron energy loss, were examined across an energy spectrum of 0–40 eV. The thermoelectric coefficients were determined utilizing the semi-classical Boltzmann transport model, assuming that the relaxation time remains constant. The results show that the figure of merit is about 0.9 at 600 K.

We systematically analyzed the elastic, thermodynamic, and directional thermoelectric properties of a set of double perovskites, specifically Ba2NbAsO6, Ba2NbSbO6, and Ba2NbBiO6. We investigated the dependence of volume, bulk modulus, thermal expansion coefficient, Debye temperature, entropy, isobaric and isochoric heat capacities, and lattice thermal conductivity on temperature and pressure using the quasi-harmonic Debye model. We analyzed the thermoelectric parameters, including the Seebeck coefficient, thermal and electrical conductivity of holes and electrons, figure of merit, and power factor, in the xx, yy, and zz directions, through the quasi-classical Boltzmann model. The findings demonstrate a figure of merit exceeding 0.8 across a wide range of charge carrier concentrations and a Seebeck coefficient greater than 0.9 mV/K, making Ba 2NbAsO6, Ba2NbBiO6, and Ba2NbSbO6 compounds promising candidates for heat-to-electricity conversion applications. We assessed the mechanical stability and characteristics, including bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, Debye temperature, and the velocities of longitudinal, transverse, and average sound propagation, derived from
the single-crystal elastic constants Cij, which were evaluated numerically using the strain-stress technique.

This work investigates the magnetic stability, structural, electronic and optical properties of the double perovskite compound NbFePb2O6.The PBE-GGA function is used to evaluate the structural parameters and verify the magnetic stability among ferromagnetic, paramagnetic and antiferromagnetic states. The compound exhibits ferromagnetic behavior with negative formation enthalpy and positive cohesive energy. The investigation further reveals the compound’s semiconducting character with a direct band-gap of 3.40 eV (L-L) in the spin-up state, and an indirect band-gap of 1.87 eV (Γ-X) in spin-down state. The study extends to the compound’s response to light incidence, encompassing the calculation of the real and imaginary parts of the dielectric function, the absorption coefficient, the reflectivity and refractivity coefficients, as well as the optical conductivity. The comprehensive analysis yielded results that underscore the compound’s suitability for photovoltaic applications, attributable to its semiconducting nature and the optical properties it exhibits.

Based on the density functional theory, the double half-Heusler alloys LuXCo2Bi2 (X = V, Nb, and Ta) were studied to predict their structural, thermodynamic, thermoelectric, and optical characteristics. All the considered alloys are thermodynamically stable and have semiconductor behavior with indirect band gaps of 0.62, 0.75, and 0.8 eV for LuVCo2Bi2, LuNbCo2Bi2, and LuTaCo2Bi2, respectively. The investigated compounds exhibit semiconducting behavior with energy gaps below 0.8 eV. The impact of heat and pressure on thermodynamic coefficients was evaluated, and the influence of charge carriers on the temperature-dependent properties was studied using the semi-classical Boltzmann model. The studied compounds were characterized by their low lattice thermal conductivity at room temperature and low thermal expansion coefficient. These alloys exhibit substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region, making them highly appealing materials for applications in the energy and electronics sectors.

This study provides crucial information on the fundamental physical characteristics of Ba2NbBO6 (B = As, Sb, and Bi) double perovskites with rhombohedral structure. These compounds are thermodynamically stable in their rhombohedral shape over a pressure range of −20–30 GPa. Electronic structure calculations revealed that Ba2NbAsO6, Ba2NbSbO6, and Na2NbBiO6 are semiconductors with energy bandgaps of 2.101 eV, 1.71 eV, and 2.813 eV, respectively. By analyzing the calculation results from the quantum theory of atoms in molecules, it is expected that the Nb-O and As/Sb/Bi-O bonds to have covalent features. In contract, Basingle bondO and Basingle bondAs/Sb/Bi bonds exhibit ionic characteristics. We also determined the real and imaginary parts of the dielectric function, absorption coefficient, optical conductivity, loss energy function, reflectivity, refractive index, and extinction coefficient as function of the incident light energy.

The present work involves a computational investigation of the elastic, thermal, and thermoelectric characteristics of Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6 from the Double Perovskite family. The study verified the mechanical stability of the three compounds and investigated Young’s modulus, Poisson, bulk, and shear modulus in various stress orientations. We were also able to compute longitudinal, transverse, and average sound velocities (Vl, Vt, and Vm, in m/s), and the findings revealed that Sr2MnReO6 had a greater longitudinal velocity than the other two compounds. Thermodynamic characteristics revealed that Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6exhibit low lattice thermal conductivity (Kl) at medium temperatures, strong heat absorption, and a moderate coefficient of thermal expansion.The analysis of the electron and hole charge carriers’ transport characteristics revealed that, when doped with an electron concentration close to 1020 cm−3, the two materials, Ba2MnReO6 and Sr2MnReO6, may have an excellent figure of merit surpassing 0.6 at temperatures over 600 K.

Several exchange–correlation potentials within the framework of Density Functional Theory (DFT) were used to study the structural, electronic, magnetic, optical, and thermoelectric properties of cubic perovskites CsEuX3 (X=Cl, Br, and I). The exchange–correlation potentials used in this study include GGA, mBJ, and GGA+U, both with and without spin–orbit coupling (SOC). The stability of all compounds was confirmed by the obtained values of the cohesive energy, formation energy, and tolerance factor. When GGA+U with SOC is used, all compounds show direct bandgap with no effect of the spin state on the bandgap value. The bandgap varies differently for spin-up and spin-down states under pressure. Europium ions control the magnetic properties. Optical investigations indicate that CsEuBr3 and CsEuI3 exhibit identical characteristics, whereas CsEuCl3 has a similar trend but shifted to higher energy. Absorption mostly takes place in the UV region, whereas there is about 20 % reflectance in the infrared (IR) and visible regions. All compounds have low energy loss and excellent transparency. Our investigation indicates that the present compounds are good thermoelectric materials with a high figure of merit. For example, CsEuCl3 demonstrates a figure of merit (ZT) ranging from 0.82 to 0.86 for spin-up and around 1 for spin-down over the temperature range 50–800 K. Such encouraging results indicate that all compounds are potential candidates for optical applications and thermoelectric devices.

We present and analyze the findings of a comprehensive ab initio computation that examines the electronic, optical, and thermoelectric characteristics of a recently synthesized Zintl compound known as CsGaSb2. The electronic and optical characteristics were examined using the DFT-based FP-L/APW+loapproach. Toaddress the exchange–correlation effects, we employed the GGA-PBEsol and TB-mBJ approaches.The CsGaSb2 semiconductor exhibits an indirect bandgap of 0.695 eV when analyzed with the GGA-PBEsol approach, and a bandgap of 1.254 eV when analyzed with the TB-mBJ approach.The PDOS diagrams were used to discover the origins of the electronic states that make up the energy bands. The charge density study reveals that the Ga-Sb link within the [GaSb2] block is mostly governed by a covalent character, whereas the cation Cs+ and polyanion [MSb2]−bonding is predominantly ionic. The frequency dependence of macroscopic linear optical coefficients was evaluated over a broad range of photon energies from 0 to 25 eV. The thermoelectric characteristics were investigated via the Boltzmann kinetic transport theoryassuming a constant relaxation time.The compound's figure of merit at a temperature of 900 K is roughly 0.8.

Density functional theory with the Hubbard corrective coefficient for the cobalt (Co) and iron (Fe) atoms was adopted to calculate the structural, dynamic, and magnetic properties of the KCoF3 and KFeF3 perovskites. The Hubbard coefficients for Fe and Co atoms were calculated using the Madsen method and their value are 3.456 eV and 4.025 eV, respectively.The structural stability of these compounds was verified by calculating their negative enthalpies of formation at the most stable state and under the influence of pressure up to 30 GPa. Their dynamic stability was confirmed via the calculation of the phonon dispersions along the high symmetry lines in the first Brillouin region. The temperature dependence of the thermal expansion coefficient, isochoric heat capacity, entropy, and lattice thermal conductivity were calculated for various fixed pressures of 0, 10, 20 and 30 GPa. Temperature dependence of the single crystal and polycristalline elastic moduli were predicted for a temperature range of 0–1000 K.

CsZnX3 (X = F, Cl, Br, I) cubic perovskite compounds were investigated using Wien2K with PBE and mBJ energy exchange potentials to determine their structural, electronic, optical, thermoelectric, and thermodynamic properties. The results of Phonon vibrational frequency, formation energy, and cohesive energy show that all compounds are stable. The electronic properties revealed that CsZnF3 has the highest indirect bandgap as an insulator, followed by CsZnCl3 and CsZnBr3, and CsZnI3 has the lowest indirect bandgap. CsZnX3 (X = Cl, Br, I) are classified as p-type semiconductors based on their electronic structure and the positive values of the Seebeck coefficient. High transparency was shown by low visible and infrared absorption. The investigated compounds exhibit high power factor and high figure of merit (ZT), which exceeds 0.7 over the temperature range 300–800 K. As the material’s temperature rises, its lattice heat conductivity decreases in accordance with thermodynamics. However, when the temperature exceeds the Debye temperature, the volume heat capacity matches the Dulong-Petit limits and the experimental results.

This study evaluated the characteristics of the compounds Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6 from the Double Perovskites family using density function theory. The acquired data suggested that these three compounds are thermodynamically stable under pressures of up to 15 GPa, with bulk modulus surpassing 160 GPa. Furthermore, these compounds exhibited magnetic properties, with total magnetic moments of 3.95, 1.94, and 3.3μB for Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6, respectively. In terms of electrical behavior, the three compounds were found to have an energy gap of 2.0, 3.0, and 1.2 eV in the spin-up (majority) channel of Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6, respectively, whereas they exhibited a metallic spin in the spin-down state. Several optical properties of the three compounds were also verified, such as absorption coefficient, refraction and reflection coefficients, optical conductivity, as well as the loss energy.

In this study, we present a comprehensive exploration of the Delafossite composites using density functional theory (DFT) and the semi-classical Boltzmann simulations within the Wien2k framework. Our investigation includes structural, electronic, magnetic and thermal properties in the tetragonal phase, providing a holistic understanding of these materials. Firstly, the structural-magnetic stability of XMnZ2 (X = Au, Hg, and Tl, Z = S, Se) was verified through ground-state energy calculations obtained from structural optimizations. Our results indicate a stable ferromagnetic phase for the six compounds. Moving on to electronic properties, we utilize the Trans-Blaha modified Becke Johnson (TB-mBJ) functional potential to elucidate the electronic behavior (metallic, half metallic, semiconductor or insolating) of the considered compounds in both up and down spin directions. Furthermore, spin-polarized band structures unveil a net magnetism in the range of 2.67μB to 4.02μB, highlighting the potential for spintronics applications. Finally, we investigate the thermodynamic properties using the quasi-harmonic model, where heat capacities at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient are analyzed and discussed under both pressure and temperature effects. Overall our study provides a comprehensive understanding of the multifaceted properties of Delafossites, paving the way for their potential applications in various fields.

A comprehensive examination of the crystal structure, as well as elastic and thermal properties, of the recently created Zintl phase CsGaSb2 has been carried out using ab initio density functional theory pseudo-potential plane-wave calculations. All the provided facts presented are newly forecasted, with the exception of the structural properties under normal conditions. The calculated lattice parameters and interatomic bond lengths of the investigated material closely correspond to the actual values, indicating a high level of accuracy. Forecasts have been generated for the elastic parameters and related characteristics of both single-crystal and polycrystalline phases of CsGaSb2. The parameters encompassed in this list are elastic constants, shear modulus, bulk modulus, Poisson’s ratio, Young’s modulus, anisotropy indices, elastic wave velocities, Pugh’s criterion, and Debye temperature. The mechanical and dynamic stability of CsGaSb2 as well as its elastic anisotropy have been established. The temperature dependence of various macroscopic properties, including bulk modulus, unit cell volume, volumetric thermal expansion coefficient, isochoric and isobaric thermal capacities, Debye temperature, Grüneisen parameter, and entropy function, was evaluated at specific pressures using Debye’s quasi-harmonic approach in combination with ab initio calculations.

Cs2AgXBr6 (X = S, Se, and Te) double perovskite structural, electronic, and optical properties were investigated using the density functional theory (DFT) method combined with various correlation potentials such as TB-mBJ, LDA, PBE, WC, and hybrid functionals (YS-PBE0). The calculated structural and elastic properties revealed that the Cs2AgXBr6 compounds are elastically stable, ductile, anisotropic, and ionically bonded. Both Poisson ratio and Pugh ratio confirm that Cs2AgXBr6 (X = S, Te, Se) compounds are ductile. The calculated density of States (DOS) and the electronic band structures of the investigated compounds display zero band gaps for these compounds. Therefore, the calculated electronic properties of these compounds indicate their metallic nature. The calculated optical transmittance shows the transparent behaviors of studied compounds.

We report an analysis of the structural, electronic, mechanical, and thermoelectric properties of oxide double perovskite structures, specifically the compounds Ba2MgReO6 and Ba2YMoO6. Our study employs first-principles density functional theory (DFT) as the investigative methodology. The electronic attributes of the examined compounds are explained by investigating their energy bands, as well as the total and partial density of states. The computational evaluation of the electronic band structure reveals that both compounds exhibit an indirect band gap semiconductor behavior in the spin-down channel, while demonstrating metallic properties in the spin-up channel. The magnetic attributes indicate a ferromagnetic nature, thus categorizing some double perovskite compounds as materials displaying half-metallic ferromagnetism (HM-FM) in addition to some other properties such as metallic and semiconductor in paramagnetic or antiferromagnetic states. The outcomes derived from the analysis of elastic constants confirm the mechanical robustness of the studied double perovskite compounds. Notably, the computed data for bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2MgReO6 surpass those of Ba2YMoO6. The calculated ratio of Bulk to shear modulus (B/G) indicates that both compounds possess ductile characteristics, rendering them suitable for device fabrication. Furthermore, both compounds display outstanding electronic and elastic properties, positioning them as promising contenders for integration within mechanical and spintronic devices. Finally, we investigate into the thermoelectric potential by evaluating parameters such as the Seebeck coefficient, electrical conductivity, thermal conductivity, figure of merit, and power factor. This assessment is conducted using the semiclassical Boltzmann theory and the constant relaxation time approximation, implemented through the BoltzTraP code. The results indicate that the investigated double perovskite oxides hold promise for utilization in thermoelectric applications.

The cubic perovskites CsGeBr3-nIn (n = 0, 1, 2, 3) were investigated using the density functional theory (DFT) for their structural, electronic, and optical properties. The present DFT calculations are carried out using three models for exchange-correlation potential, namely PBE, mBJ, and YS-PBE0. The bandgap decreases in the above sequence of compounds except CsGeBrI2, which reveals the smallest bandgap. The mBJ approximation has a larger bandgap than the PBE and smaller than the YS-PBE0. Results of calculations within the YS-PBE0 approach for CsGeBr3 and CsGeI3 agree well with QSGW + SO results. The CsGeBr3-nIn compounds are direct bandgap semiconductors and CBM and VBM are positioned at the R point and determined mainly by Ge s-states and Br(I) p-states, respectively. Analysis of optical properties shows that the DFT calculations within the PBE model consistently produce the highest static dielectric function values, while the YS-PBE0 method gives the smallest values. The curves of optical coefficients shift toward lower energies when decreasing the Br atoms in CsGeBr3-nIn. The studied compounds are semitransparent in the infrared and visible regions and show promising potential for photovoltaic applications, including solar cells.

The Delafossite group of oxide materials was initially uncovered in 1965, comprising a category of ternary compounds characterized by the general formula ABO2, with A and B denoting metallic elements. One of the most prevalent Delafossites is CuAlO2, which stands as a p-type semiconductor known for its remarkable electrical conductivity and transparency across the visible and near-infrared regions of the electromagnetic spectrum [1–3]. These distinctive qualities have propelled Delafossite materials into the spotlight for a wide array of applications, including use in electronic devices, energy storage, energy conversion, and optoelectronics. Their intriguing electronic, magnetic, and optical attributes have only recently garnered attention [4,5], prompting researchers to delve into these materials, not only to grasp their fundamental properties but also to uncover potential applications. Density functional theory (DFT) calculations have unveiled a range of electronic band structures within Delafossites, varying from metals to semiconductors contingent upon the specific choice of A and B ions. Furthermore, DFT calculations have forecasted that particular Delafossites, such as CuCrO2 and CuFeO2[6,7], manifest antiferromagnetic ordering due to the interplay of spins on the transition metal ions. In an ab initio study conducted by Azmat et al. [8], it was demonstrated that CuXO2 compounds (where X represents Al, Ga, In, B, La, Sc, Y) display semiconductive behavior. Experimental investigations into Delafossites have encompassed the electronic and optical properties. Among the most renowned Delafossites is CuAlO2, renowned for its high electrical conductivity and optical transparency. CuAlO2 boasts exceptional carrier mobility and low carrier concentration, making it an ideal candidate for transparent conductive electrodes in optoelectronic devices. Additionally, Delafossites have undergone scrutiny for their photovoltaic potential, with CuInO2 and CuGaO2 exhibiting promising results for solar cell applications. An experimental study by Kushwaha et al. [9] explored the PdRhO2 compound, revealing its crystallization in a rhombohedral-type structure characterized by crystal cell dimensions of a = 3.0240 Å and c = 18.096 Å.
In this study, we perform first-principles calculations based on density functional theory and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties for BrCdO2 in the Tetragonal phase. To compute the structural properties, the Wang and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used as exchange-correlation potentials. Besides, the modified Becke-Johnson functional of Tran and Blaha (TB-mBJ) are used to compute the electronic and optical properties to achieve the best band gap energy values and a higher degree of precision. Our calculations have revealed that this compound have direct band gap 4.17 eV. As a result of this study, BrCdO2 is promising material for optoelectronic devices, especially as photovoltaic materials in solar cells.

ABO2 is a type of Delafossite compound that has been investigated for their electronic properties, such as high electrical conductivity and magnetic behavior; make them promising candidates for use in electronic devices. In this study, we perform first-principles calculations based on density functional theory and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties for MgNiO2 in the Tetragonal phase. To compute the structural properties, the Wang and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used as exchange-correlation potentials. Besides, the modified Becke-Johnson functional of Tran and Blaha (TB-mBJ) are used to compute the electronic and optical properties to achieve the best band gap energy values and a higher degree of precision. Our calculations have revealed that this compound have direct band gap 1.79 eV. As a result of this study, MgNiO2 is promising material for optoelectronic devices, especially as photovoltaic materials in solar cells.

We used the pseudopotential plane wave approach, as implemented in the Quantum Espresso program, to
investigate the impact of X atoms (V, Nb, and Ta) on the physical properties of LuXCo2Sb2 double half Heusler
alloys. We determined the equilibrium structural parameters, including the crystal lattice parameters, atomic
position coordinates, and bulk modulus, with and without including the spin-orbit effects. The predicted singlecrystal
elastic constants (Cij) show that the title compounds are mechanically stable with a pronounced elastic
anisotropy. The bulk modulus, shear modulus, Young’s modulus, Poisson coefficient, Debye temperature, and
Vickers hardness coefficient were deduced from Cij via the Voigt-Reuss-Hill approximations. We also determined
the variations of some macroscopic physical parameters as functions of temperature and pressure, namely the
thermal expansion coefficient, lattice thermal conductivity, heat capacity at constant volume, Debye temperature
and entropy. The considered alloys demonstrate special thermal properties under pressure and heat conditions,
specifically, their low thermal expansion coefficient and lattice thermal conductivity; their thermal expansion
coefficient is lower than 4.5 × 10􀀀 5 K􀀀 1 at 1000 K, and lattice thermal conductivity don’t exceed 1 W.m􀀀 1 K􀀀 1
for temperatures higher than 300 K. Furthermore, we investigated the temperature and charge carrier concentration
dependencies of some thermoelectric coefficients. The results of this study reveal the potential of the
considered compounds for achieving a figure of merit greater than 0.5 at a temperature of 500 K and a doping
concentration of 1020 cm􀀀 3.

The primary objective of this study is to investigate the influence of spin-orbit coupling and atom type on the electronic, optical, and thermoelectric properties of LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler alloys. To achieve this, calculations were performed using the full potential linearized augmented plane wave method within the framework of density functional theory. Both full relativistic and scalar relativistic calculations were employed. The exchange-correlation interactions in this study were modeled using the PBEsol version of the generalized gradient approximation when calculating the structural ground state parameters. For the analysis of electronic, optical, and thermoelectric properties, the modified Becke–Johnson potential was employed. The modified Becke–Johnson potential was specifically chosen for its capability to improve the description of band gaps, particularly for systems with small band gaps, such as the LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler materials examined in this study. This potential offers a more accurate representation of the electronic properties, enabling a more reliable analysis of the optical and thermoelectric characteristics of the materials under investigation. The examined LuXNi2Sn2 (X = V, Nb, and Ta) materials exhibit semiconductor behaviour, with band gaps smaller than 0.4 eV that can be controlled by varying the “X” atom. The charge carriers, specifically holes and electrons, exhibit light effective masses, indicating high mobility. Furthermore, these compounds exhibit low thermal expansion coefficients and satisfy the criteria for thermodynamic stability. In terms of optical properties, they display substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region. Considering their favourable power factor and figure of merit characteristics, the LuXNi2Sn2 (X = V, Nb, and Ta) materials possess the potential to be promising candidates for thermoelectric applications.

The primary objective of this study is to investigate the influence of spin-orbit coupling and atom type on the electronic, optical, and thermoelectric properties of LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler alloys. To achieve this, calculations were performed using the full potential linearized augmented plane wave method within the framework of density functional theory. Both full relativistic and scalar relativistic calculations were employed. The exchange-correlation interactions in this study were modeled using the PBEsol version of the generalized gradient approximation when calculating the structural ground state parameters. For the analysis of electronic, optical, and thermoelectric properties, the modified Becke–Johnson potential was employed. The modified Becke–Johnson potential was specifically chosen for its capability to improve the description of band gaps, particularly for systems with small band gaps, such as the LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler materials examined in this study. This potential offers a more accurate representation of the electronic properties, enabling a more reliable analysis of the optical and thermoelectric characteristics of the materials under investigation. The examined LuXNi2Sn2 (X = V, Nb, and Ta) materials exhibit semiconductor behaviour, with band gaps smaller than 0.4 eV that can be controlled by varying the “X” atom. The charge carriers, specifically holes and electrons, exhibit light effective masses, indicating high mobility. Furthermore, these compounds exhibit low thermal expansion coefficients and satisfy the criteria for thermodynamic stability. In terms of optical properties, they display substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region. Considering their favourable power factor and figure of merit characteristics, the LuXNi2Sn2 (X = V, Nb, and Ta) materials possess the potential to be promising candidates for thermoelectric applications.

In this work, we performed first-principles calculations based on density functional theory (DFT) and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties of PdAlO2, PdCrO2 and PdRhO2 in the Tetragonal phase. Our calculations have revealed that these three compounds have direct band gaps in the range of 1.87 to 2.58 eV. The thermodynamic properties are investigated using the quasi-harmonic model, where heat capacities at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient are analyzed and discussed under both pressure and temperature effects. As a result of this study, PdAlO2, PdCrO2, and PdRhO2 are promising materials for optoelectronic devices, especially as photovoltaic materials in solar cells. In doing so, we computed for each compound the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and figure of merit in the temperature range from 300 K to 500 K. The relaxation time and lattice thermal conductivity are calculated as well. Our results reveal that low thermal conductivity and high Seebeck coefficient can be achieved at the same time. In addition, they exhibit a higher Seebeck for PdAlO2 compared to PdBO2 (B= Cr and Rh) up to 1.6 mV/K for ‎PdAlO2 at 300 K. Thereby improving their thermoelectric performance which makes them attractive thermoelectric materials at high temperatures.

Ab initio calculations based on density functional theory were performed to determine the structural parameters
of the LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler compounds and verify their thermodynamic stability in
an orthorhombic structure as well as to predict their electronic and optical properties. The predicted electronic
band structures show that LuVCo2Sb2, LuNbCo2Sb2, and LuTaCo2Sb2 are semiconductors with indirect bandgaps
of 0.728, 0.845, and 0.898 eV, respectively. The effective masses calculated at the valence band maximum at the
conduction band minimum show a strong anisotropy. It can be seen that electrons are lighter than holes. The
nature of the electronic states involved in the formation of the energy bands has been determined thanks to the
density of states calculations. The character of chemical bonds was analyzed through the charge density distribution
map. Linear optical functions, namely complex dielectric function, absorption coefficient, optical
reflectivity and refractive index, were calculated for all compounds in an energy range up to 20 eV. The
calculated optical spectra exhibit a noticeable anisotropy. The compounds under consideration are characterized
by strong absorption of incident electromagnetic radiation in a wide energy range.

Due to their useful physical properties, copper-based chalcogenides materials are recently promising for numerous emerging technological fields. In photovoltaics, discovering and designing suitable materials for solar cells is a primary technical challenge. The structural, electrical, optical, and thermoelectric properties for both CuYSe2 and CuYTe2 in the hexagonal phase, as well as CuYS2 in the orthorhombic phase have been investigated using a numerical Full Potential-Linearized Augmented Plane Wave (FP-LAPW) technique based on Density Functional Theory (DFT).

To compute the structural properties, both, the local density approximation (LDA) and the generalized gradient approximation (PBE-GGA) were used as exchange-correlation potentials. On the other hand, the modified Becke-Johnson (mBJ) was used to compute the optoelectronic, properties with higher degree of precision. Our calculations revealed that these three compounds have indirect band gaps in the range of 0.6 eV–2.1 eV. Moreover, numerous thermoelectric qualities of the investigated compounds estimated as a function of chemical energy at different temperatures using the semi-local Boltzmann transport theory, whereby the findings exhibit a higher Seebeck coefficient for CuYS2 compared to CuYZ2(Z = Se and Te) up to 2.7 mV/K for CuYS2 at 300 K, with acceptable values of thermal and electronic conductivity. The quasi-harmonic model is used to examine thermodynamic properties such as heat capacity at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient under both pressure and temperature influences. As a result of this study, CuYS2, CuYSe2 and CuYTe2 are promising materials for optoelectronic devices, especially as photovoltaic materials in solar cells.

Electronic, magnetic, dynamic, elastic, thermodynamic, and thermoelectric properties for Co2-based full Heusler alloys are investigated theoretically. The full potential–linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) incorporated on WIEN2k code is employed in our calculation. Through this study, we found that the FM-L21 is the most magnetic-structure stable phase for both Co2ZrAl and Co2ZrSi compounds, as well as they, are dynamically stable where all the calculated of the optic and acoustic phonon frequencies have positive values. Band structure calculation demonstrated that all compounds exhibit band gaps of about 0.88 and 1.54 eV using mBJ-GGA potentials for Co2ZrAl and Co2ZrSi in a localized minority spin channel (unlike the other direction which appears a metallic behavior) with high spin polarization (100%) in its ground state. Under high pressure, both compounds keep the same electronic behavior in both spins’ channels with a little decreasing in gap energy, unlike the total magnetic moment which doesn’t change. The semi-local Boltzmann transport theory has been used to investigate thermoelectric properties and we found that both compounds exhibit a high Seebeck coefficient and high-power factor up to 1.25 mV/K for Co2ZrSi. Also, the quasi-harmonic model has been applied to study the temperature effect on heat capacities at constant volume, in which entropy, Debye temperature and lattice thermal conductivity are analyzed and discussed. To get more information about the elastic behavior; the elastic stability in the equilibrium state and under two pressures values (12 GPa and 24 GPa) are found. The findings predicted the stability of these compounds’ properties with and without pressure, which makes them candidate materials for devices fabrication in several areas such as spinotronic, thermoelectric, shape-memory and spin filters.

We used density functional theory based calculations to investigate the structural and optic properties of copper-based ternary chalcogenide Cu-M-X (M : Sb, Bi & X : S, Se). These form orthorhombic crystallographic structure with Pnma space group. The calculated electronic band structure is indirect for all these compounds in conjunction with a close direct band gap transition. Interestingly, a very high optical absorption coefficient above 105 cm-1 above band gap values is noticed for these materials, making them suitable for ultrathin solar cell absorbers.