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Spintronics is a rapidly developing field in advanced technology. It focuses on manipulating the spin of electrons to achieve high-speed data transfer, handling, and storage in order to enhance its capabilities. We conducted a systematic investigation of the ferromagnetism, electronic, and thermoelectric characteristics of spinel compounds LiFe 2 (O/S) 4. Our analysis for optimization demonstrates that ferromagnetic states exhibit great energy release compared to the antiferromagnetic states, indicating the presence of ferromagnetic behavior in the studied compounds. To evaluate the presence of ferromagnetism above room temperature, we employ the Heisenberg model to calculate the Curie temperature and spin polarization to evaluate the presence of ferromagnetism above room temperature. Additionally, a concise overview of the nature of ferromagnetism, including band structures, density of states, exchange energies and constants, hybridization double exchange model, and crystal-field energy, is provided in this research. The absorption of a shift in magnetic moment from Fe to the Li and O/S sites suggests that the ferromagnetic behavior is primarily due to the spin of electrons. Furthermore, we explore the impact of the thermal parameters on the electro-spin as well as the thermoelectric characteristics for both spin-down and spin-up states, providing insights into the energy-harvesting potential. • Half-metallic ferromagentic spinels LiFe 2 (O/S) 4. • Elastic constant are investigated for structural stability. • Electronic and magnetic properties for spintronic applications. • Magnetic moments are discussed for both compounds. • The electronic and lattice thermal conductivity are calculated for thermoelectric characteristics. [ABSTRACT FROM AUTHOR]

Mechanical, spin-polarized electronic, and transport characteristics of rare-earth-based MgSm 2 Y 4 (Y S, Se) spinels are investigated using first-principle calculations. In contrast to the anti-ferromagnetic and nonmagnetic states of MgSm 2 Y 4 (Y S, Se), the optimization study reveals that ferromagnetic states release more energy, and optimized lattice constants in ferromagnetic states are comparable to existing values. Phonon dispersion and formation energy are also calculated to confirm the dynamical stability stability. The ductile character is confirmed by investigating the Poisson's and Pugh ratios, and the values of other elastic parameters show their importance for the manufacturing of devices. Heisenberg model and the density of electron states at the Fermi level report the Curie temperature and the spin polarization. Spin-polarized electronic properties indicate half-metallic ferromagnetic because the spin-down reflects a semiconductor nature, whereas the metallic nature manifests the spin-up. The total magnetic moments are generated through hybridization of chalcogenide 2p-states and the Sm f-states. We found that the studied spinels may be used in thermoelectric devices by examining transport characteristics such as electronic and phononic thermal conductivity, Seebeck co-efficient, and figures of merit (ZT). Our results indicate that the ZT for MgSm 2 S 4 is almost three times the ZT obtained for MgSm 2 Se 4. • Half-metallic ferromagentic spinels MgSm 2 Y 4 (Y S, Se). • Phonon dispersion are investigated for dynamical stability. • Electronic and magnetic properties for spintronic applications. • Magnetic moments are discussed for both spinels. • The ZT for MgSm 2 S 4 is almost three times the ZT obtained for MgSm 2 Se 4. [ABSTRACT FROM AUTHOR]

Full potential LAPW + lo method is used for exploring electronic, structural and thermoelectric properties for MgNd 2 X 4 (X = S, Se) spinels that are found to show ferromagnetic-semiconductor behaviour in the spinel structure. The investigated negative value of formation energy and positive value of phonon spectra computed using PBEsol GGA indicates the energetic and dynamical stability of the studied cubic ferromagnetic-semiconductors. We have used TB-mBJ potential functional for electronic and magnetic properties, which lead to a reliable account of electronic structure, demonstrating band occupancy in the spinels along with a clear explanation of density of states. The stability of ferromagnetic state in the studied materials is because of the exchange splitting of Nd cations based on p-d hybridization which is in accordance with the results obtained for electronic band structure and density of states. The exchange splitting of bands can be justified by the spin magnetic moment between anions and cations, and sharing of charge. The computed values of dielectric constant and their associated optical parameters are used to explain the optical active behaviour of the spinels under investigation; indicating that the two spinels studied in the present work are suitable for solar cells device applications. The calculation of thermoelectric properties is very useful for determining a material's potential use in waste energy recovery systems and many other innovative applications. [ABSTRACT FROM AUTHOR]

• Theoretically examined the physical features of DPs Li 2 CuBiZ 6 (Z = Cl, Br, I). • Elastic properties are investigated for structural stability. • Electronic and optical properties for solar applications. • The dispersion of light is explained by ε 1 (ω). • Due to its higher Seebeck coefficient, Li 2 CuBiCl 6 possessed a larger power factor than Li 2 CuBiBr 6 and Li 2 CuBiI 6. Due to their potential applications for optoelectronic and thermoelectric devices, Li-based double perovskites (DPs) have been widely investigated. In current article, we theoretically examined the mechanical, optoelectronic and thermoelectric features of DPs Li 2 CuBiZ 6 (Z = Cl, Br, I). We employ the generalized gradient approximation (PBEsol) for examining the structural and elastic characteristics of these compounds, while the modified Becke-Johnson (mBJ) functional is used for obtaining an improved accord of the thermoelectric and electronic characteristics with experimental observations. For the stability of all DPs, the Born Criteria and formation energy are investigated. The cubic symmetry's elastic constants are examined to determine the difference between ductile and brittle nature, anisotropy, and Debye temperatures. The bandgaps are 2.0 eV, 1.7 eV, and 1.3 eV, for Li 2 CuBiCl 6 , Li 2 CuBiBr 6, and Li 2 CuBiI 6 , respectively, as determined by the mBJ potential. All DPs were also examined regarding optical absorption, refractive index, and dielectric constants for the energy range 0–10 eV, ensuring the absorption among visible regions. Furthermore, all DPs are appropriate candidates for thermoelectric applications due to the lower lattice thermal, higher Seebeck coefficient, thermal conductivity, and Figure of merit (ZT), which are all elucidated by Boltzmann classical theory. [ABSTRACT FROM AUTHOR]

Magnesium based spinel chalcogenides MgY 2 Z 4 (Z = S and Se) have recently become a focus of renewed research interest owing to their high magnesium mobility; making them potential candidates for Mg batteries. In addition, the existence of a >1 eV band gaps in MgY 2 Z 4 compounds also make them interesting for opto-electronic device operating in the visible to UV range of electromagnetic spectrum. Our calculations indicate that the electronic properties computed using the mBJ-LDA + SOC are in good agreement with earlier DFT calculations. The optical properties of the two compounds are examined as a function of incident photon energy, which indicate that these materials can be utilized in optical devices operating in visible and UV region of electromagnetic spectrum. The transport properties are also computed using BoltzTrap code where the variation of electrical conductivity, thermal conductivity and Seebeck coefficient with chemical potential and temperature is examined. Image 1 • DFT calculations are performed for magnesium based spinel chalcogenides MgY 2 Z 4 (Z = S and Se). • Structural parameters depict that when we change Z from S to Se, the lattice parameter increase. • The electronic properties are computed using the mBJ-LDA+SOC. • Calculated optical properties show device applications in visible and UV region. • Electronic transport properties show that these spinels can be used even at elevated temperatures. [ABSTRACT FROM AUTHOR]

Methods based on density functional theory are used to evaluate the thermodynamic, mechanical, optoelectronic and thermoelectric properties of the alkali metal-based iodides: XGeI 3 (X = K, Rb and Cs). The thermodynamic stability of these compounds is checked by negative formation energy, and mechanical stability tested through tensor analysis of Chapin's method. For optoelectronic and thermoelectric properties, the recently developed modified Becke–Johnson potential is applied for accurate analysis of bandgap values. The optical properties are explored in terms of dielectric constants and refraction, while thermoelectric properties are explained by electrical and thermal conductivities, Seebeck coefficient, power factor and figure of merit scale. The narrow bandgap, high value of light absorption in the visible region and thermoelectric efficiency make XGeI 3 prospective materials for renewable energy applications. • We elucidate physical properties of alkali metal-based iodides [XGeI 3 (X = K, Rb, and Cs)]. • We confirm thermodynamic stability of studied compounds by enthalpy of formation. • Thermoelectric properties of spinel oxides determined using BoltzTraP code. • Narrow bandgap and thermoelectric efficiency give XGeI 3 potential in renewable energy applications. • These materials are suitable for use in thermoelectric devices. [ABSTRACT FROM AUTHOR]

For leading spintronic technology, the significance of rare earth in the spinels chalcogenide MgCe 2 Z 4 (Z = S, Se) has been investigated. Wein2K and BoltzTraP program packages are used to calculate the magnetic and transport characteristics of the spinels. While comparing the energies within the ferromagnetic and nonmagnetic states, the ferromagnetic state stability in the ground state is examined. The formation energy, phonon dispersion curve, and mechanical stability conditions help clarify the issue of stability in the cubic ferromagnetic phase. Poisson's and Pugh's ratios are employed to ensure the brittle characteristics. To explore the electronic properties, modified Becke and Johnson (mBJ) potential are utilized to investigate both spinels' direct narrow bandgap (spin up channel) nature. Chalcogenide's 2p produces the total magnetic moments- and rare-earth metals' f-states, which result in significant hybridization around the Fermi level. The computed total magnetic moment integer values and polarization are used to demonstrate spin polarisation. Finally, the Seebeck coefficient, thermal-to-electrical conductivity ratio, and power factor are used to evaluate thermoelectric properties. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the physical aspects of the cubic phase XCrO 3 (X = Ca , Sr , Ba) perovskites are studied by employing full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method. These compounds have been found stable in ferromagnetic (FM) phase since they possess lower energy in FM phase compared to non-FM phase and their stability is also confirmed by calculating the enthalpy of formation (ΔH). The electronic structures of these compounds are analyzed with Trans and Blaha modified Becke–Johnson potential (TB-mBJ) for both spin up and spin down channels, which indicate their half-metallic characters. Analysis of density of states (DOS) shows major contributions of O-2 p states in the valence band and Cr 3 d -state in conduction band. A comparative analysis of crystal field effect (Δ E crystal) and the exchange energies (direct Δ x (d) and indirect Δ x (p d)) tells about the main part of electronic spin in ferromagnetic character. The calculated magnetic moments make these compounds favorable for spintronic applications. In the end, thermoelectric parameters are computed for 200 K–800 K temperature range to explore potential of these compounds for applications in renewable energy devices. Highlights • To elucidate the structural, electronic, magnetic and thermoelectric properties of cubic XCrO 3 (X = Ca , Sr , Ba) oxides. • We investigate magnetic properties by computing the Δ E crystal , Δ x (d) direct and indirect Δ x (p d) energies. • Thermoelectric properties of spinel oxides have been computed by using BoltzTraP code. • Finally scrutinize that these materials are used in the thermoelectric device. [ABSTRACT FROM AUTHOR]

The electronic, optical and thermoelectric analyses of BaGeO 3 perovskite have been done by using density functional theory (DFT) based Trans and Blaha modified Becke and Johnson (TB-mBJ) approach. The applied pressure (up to 30 GPa) has been found tailoring the band gap from indirect to direct bandgap (at 20 GPa), within the visible region, revealing renewable energy applications of the studied perovskite. The applied pressure improves mechanical stability by increasing ductility. Furthermore, optical properties are illustrated by computing dielectric constants, refraction, absorption, optical conductivity and optical loss factor for suggesting optoelectronic applications. The maximum peaks shifting to higher energy, due to increasing pressure indicate a blue shift. Finally, the calculated thermal and electrical conductivities, See-beck coefficient, power factor, Hall coefficient, specific heat capacity, susceptibility and electron densities are also elaborated for thermoelectric applications by using BoltzTraP code. [ABSTRACT FROM AUTHOR]

The density functional theory based full-potential linear-augmented-plane-wave plus local-orbital method has been used to study the physical properties of PbSnO 3 in hypothetical cubic perovskite. An external pressure up to 40 GPa has been applied on PbSnO 3 to realize the variation in its electronic band structure and the subsequent optical properties. The stability of the PbSnO 3 has been investigated by the mechanical properties, the enthalpy of formation and Goldschmidt tolerance factor. Moreover, the Born criteria have been adopted to justify the mechanical stability of the PbSnO 3 perovskite. We show that the electronic bandgap of PbSnO 3 can be tailored from indirect to direct band gap at high symmetry (X-X) direction at an external pressure of magnitude ~ 26 GPa. The effect of pressure on the optical properties has been studied in terms of dielectric function, absorption, refraction, reflection, and optical loss factor. The application of hydrostatic pressure has shifted the maximum absorption toward the visible range, revealing that PbSnO 3 can be used for high- pressure optoelectronic applications. [ABSTRACT FROM AUTHOR]

The physical behavior of perovskites ATiO 3 (A=Pb, Sn) has been explored by using density functional theory based full-potential linearized-augmented-plane-wave plus local-orbital (FP-LAPW+lo) method. The lattice parameters calculated from the optimized structures by using Murnaghan equation of state and Chapin's method have been found in good agreement with the available literature that ensures the reliability of the adopted methodology. Moreover, the optoelectronic and thermoelectric properties have been elaborated by using modified Becke-Johnson exchange potential. The optical behavior has been explored in terms the dielectric constants, refractive indices, absorption spectra and optical loss factors. The absorption spectra of these materials reveal a large absorption in the visible and low ultraviolet part of incident light. The thermoelectric properties of ATiO 3 are explained in terms of electrical conductivities, thermal conductivities, power factors, and the specific heat capacities. The ATiO 3 family of pervoskites has been found to exhibit the bandgaps falling in the visible region of solar spectrum and show high values of thermal efficiency that make them potential multifunctional candidates for optoelectronic and energy harvesting applications. [ABSTRACT FROM AUTHOR]

We present the mechanical, electronic, optical and thermoelectric behaviors for BiBO 3 and BiAlO 3 perovskite crystals, which are investigated by employing density functional theory (DFT). The structural and elastic characteristics are computed by using GGA-PBEsol exchange-correlation functional, while the electronic, optical and thermoelectric properties are derived through modified Becke-Johnson (mBJ) potential. The thermal stability is calculated by using the enthalpy expression and further verified by the elastic properties. Besides the physical properties at the ground state, we also explore the effects of pressure (0–40 GPa) onBiBO 3 and BiAlO 3 , in strides of 10 GPa, on the electronic structure. Both BiBO 3 and BiAlO 3 illustrate indirect band gap (Γ-M) at 0 GPa, however, increase in pressure results in transforming to a direct (Γ-Γ) band gap at 20 GPa and 40 GPa, respectively. Under the application of pressures, complex dielectric constant and some other optical parameters are also inspected. All the computed optical properties have revealed a higher energy shift, as the applied pressure increases proposing potential optoelectronic device applications of BiBO 3 and BiAlO 3 . Finally the thermoelectric characters are elucidated by calculating the electrical conductivity, thermal conductivity and the Seebeck coefficient of BiBO 3 and BiAlO 3 compounds, which are discussed as a function of temperature. These compounds are prospective applicants for the optoelectronics and thermoelectric devices, due to their appropriate direct bandgap nature realized by applying pressure and the optimum exhibited thermoelectric behaviors, respectively. [ABSTRACT FROM AUTHOR]

In this study, we report the mechanical, structural, electronic, magnetic and optical behaviors in Zn 1−x Mn x S (0 ≤ x ≤ 1), which are determined by employing Wein2K code. The ferromagnetic (FM) state stability of the Zn 1−x Mn x S alloys has been elucidated from the calculated values of enthalpy of formation. The elastic constant (C 11 , C 12 , C 14 ) are calculated to find various useful mechanical parameters, which depend upon Mn concentrations. The calculated electronic band structure and density of states (DOS) have demonstrated that exchange splitting through p-d hybridization, arising due to Mn impurities, stabilize a ferromagnetic state. The exchange splitting of the bands is further elucidated from the sharing of magnetic moment, charge and spin, between the impurity cations and the host lattice anions. Various parameters like direct spin-exchange splitting Δ x ( d ), exchange constants N 0 α and N 0 β have also confirmed a stable ferromagnetic state. Various calculated optical parameters have indicated that the studied compounds respond to visible and ultraviolet energies. Moreover, the calculated optical band gap and static dielectric constant ɛ 1 (0) verify Penn's model. The studied compounds of Zn 1−x Mn x S have been shown theoretically that they find potential spintronic and optical device applications. [ABSTRACT FROM AUTHOR]

The spin-dependent magnetic, thermoelectric, and electronic characteristics of Mg-based spinels MgGd 2 X 4 (X = S, Se) are investigated using density functional theory (DFT) calculations. The modified Perdew-Burke-Ernzerhof generalized gradient approximation (PBEsol-GGA) is utilized to compute the structural and elastic characteristics. In addition, the magnetic, thermoelectric, and electronic characteristics are explored employing the modified-Becke and Johnson (mBJ) potential. After the energy difference calculations among the ferromagnetic (FM) and nonmagnetic (NM) phases, the stability of the structures is confirmed in the FM phase. Further, thermodynamic stability is determined by calculating formation energies and phonon dispersion spectra. The Charpin method is used to analyze elastic characteristics in detail. The total magnetic moments are produced by 2p-states of chalcogenides and f-states of Gd atoms, which result in substantial hybridization at the Fermi level. Finally, electronic-thermal coefficients, such as the power factor, Seebeck coefficient, and thermal and electrical conductivity, are investigated, concluding that investigated spinels can be used in thermoelectric devices. [ABSTRACT FROM AUTHOR]

The mechanical, electronic, optical and thermoelectric properties of cubic perovskite BiScO 3 are studied by using density functional theory. The lattice parameter of BiScO 3 calculated at zero pressure indicates good agreement with similar compounds crystallizing in the cubic perovskite structure. The exchange-correlation functional based on Perdew-Burke-Ernzerhof GGA has been used for calculating structural and mechanical properties, while the functional proposed by Tran and Blaha in the form of modified Becke-Johnson (mBJ) exchange potential has been employed to calculate the electronic, optical and thermoelectric properties. The elastic constants and bulk modulus are calculated and their pressure dependence upto 50 GPa has been investigated. Cubic BiScO 3 is found to be an indirect bandgap semiconductor at ambient pressure, while a direct bandgap appears under the influence of pressure. In addition to the electronic properties, the dielectric function, refractive index, reflectivity, extinction coefficient and absorption spectrum are also presented. Moreover, important thermoelectric properties of the compounds are explained in terms of electrical conductivity, thermal conductivity, Seebeck coefficient and figure of merit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct band gap semiconductor of Li based double perovskites halides A 2 LiInBr 6 (A = Rb, Cs) are explored in terms of density functional theory. • Structural and elastic investigation depict structural stability of A 2 LiInBr 6 in cubic phase. • The electronic band structures analysis show both materials are strong candidate for the fabrication of solar cell devices. • Optical parameters were calculated for the assurance of semiconductor behaviour. • Calculated thermoelectric parameters indicate that the both materials can be used even at elevated temperatures. We exhibit the investigation of structural, optical, thermoelectric, and electronic properties of A 2 LiInBr 6 (A = Rb, Cs) by applying density functional theory. The calculated bandgap of cubics structure using modified Becke and Johnson (mBJ) potential indicates that the bandgap reduces by replacing cations Rb to Cs. The calculated values appear in the visible energy range. Further, investigation of optical characteristics suggest that they might be used in solar cells. In addition, promising thermoelectric applications demand the small bandgap, which results from a high figure of merit for A 2 LiInBr 6. The computed small bandgap, high optical absorption, and maximum values of the figure of merit (ZT) stipulate Cs 2 LiInBr 6 applicable for solar absorbing cells and energy conversion applications. [ABSTRACT FROM AUTHOR]

The full-potential linear-augmented-plane-waves plus local-orbitals (FP-LAPW+lo) method has been employed for investigation of half-metallic ferromagnetism in Cr-doped ordered zinc-blende MgSe and MgTe semiconductors. Calculations of exchange and correlation (XC) effects have been carried out using generalized gradient approximation (GGA) and orbital independent modified Becke–Johnson potential coupled with local (spin) density approximation (mBJLDA). The thermodynamic stability of the compounds and their preferred magnetic orders have been analyzed in terms of the heat of formation and minimum total energy difference in ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering, respectively. Calculated electronic properties reveal that the Cr-doping induces ferromagnetism in MgSe and MgTe which gives rise to a half-metallic (HM) gap at Fermi level ( E F ). Further, the electronic band structure is discussed in terms of s ( p )– d exchange constants that are consistent with typical magneto-optical experiment and the behavior of charge spin densities is presented for understanding the bonding nature. Our results demonstrate that the higher effective potential for the spin-down case is responsible for p–d exchange splitting. Total magnetic moment (mainly due to Cr- d states) of these compounds is 4 µ B . Importantly, the electronic properties and HM gap obtained using mBJLDA show remarkable improvement as compared to the results obtained using standard GGA functional. [ABSTRACT FROM AUTHOR]

In this study, the special quasi-random structure (SQS) approach has been considered for structural, electronic and optical properties of rock-salt (RS) and zinc-blende (ZB) phases of ZnO 1− x Te x ( x = 0, 0.25, 0.5, 0.75 and 1) using density functional theory. The Wu–Cohen generalized gradient approximation (GGA) has been employed for optimizing the lattice parameters ( a 0 ) and bulk moduli ( B 0 ) in both phases which show reasonable agreement with numerous theoretical and experimental results. To compute the band gaps with high degree of precision, we employed Engel–Vosko GGA and modified Becke and Johnson local density approximation (mBJLDA) functionals. In the RS phase, metallic nature of the compounds under investigation is evident for 0.25 < x < 1, whereas direct band gap appears at all concentrations in ZB phase. The density of states (total and partial) are presented to comprehensively analyze the electronic structure of all compounds. Contrary to earlier theoretical studies, the mBJLDA band gap values for the end binaries appear to be significantly improved showing overall better agreement with the experimental data. The optical properties of ZnO 1− x Te x alloys in the ZB phase are also discussed in terms of dielectric function which show their potential utilization in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electronic and optical properties of the special quasi-random structure of ZnO1− x S x alloy are investigated. [•] The calculations are performed for both rock salt (RS) and zinc blende (ZB) phases. [•] The compound under study has metallic behavior in RS phase for x =0.50 and 0.75. [•] The semiconducting behavior of the compounds increases in ZB phase with doping order. [•] Optical functionality for the ZnO1− x S x alloys increases with increasing S. [Copyright &y& Elsevier]

Abstract: Structural, electronic and magnetic properties of Mn-doped BeSe and BeTe have been studied by employing the full-potential linear augmented plane waves plus local orbitals (FP-LAPW+lo) method within the spin-polarized density functional theory (DFT). The investigations are carried out by varying the Mn concentration, “x”, in BeSe and BeTe host matrices for x=0.25, 0.5 and 0.75. The results of spin-polarized calculations manifest the presence of ferromagnetic band structures with both spin-up and spin-down alignments. Our calculated results of band structures reveal that for x=0.25, 0.5 and 0.75, Be1−x Mn x Se has a half-metallic (HM) band structure profile showing 100% spin polarization at the Fermi level. On the other hand, the Be1−x Mn x Te band structure shows complete 100% spin polarization at the Fermi level only for x=0.25 and 0.5. Spin-dependent charge densities have been calculated to study the bonding nature, and the values of the exchange constants, and , are also determined which are consistent with the values from the typical magneto-optical experiment. In addition, the calculations of spin exchange splitting, , exhibit important indication regarding the attractive effective potential for minority spin rather than majority spin. For each concentration x, the value of total magnetic moment has been estimated to be 5 , which reveals that addition of Mn impurity does not affect the hole concentration of a perfect BeSe (Te) crystal. [Copyright &y& Elsevier]

Abstract: Full-potential linearized augmented plane wave plus local orbitals (FP-LAPW+lo) method within density functional theory (DFT) has been utilized to calculate structural, electronic and optical properties of Be-doped CdS, CdSe and CdTe compounds with the dopant concentration x in the range 0≤x≤1. For the contribution of exchange-correlation potential, we used Wu–Cohen generalized gradient approximation (GGA) to calculate structural parameters, whereas both Wu–Cohen and Engel–Vosko GGA have been applied to calculate electronic structure of the materials. Only a slight deviation from Vegard''s law has been observed for the calculated lattice constants and bulk moduli of the alloys. Structural and chemical factors that affect the band-gap bowing of these semiconductor alloys have been estimated and discussed. Density of states curves and charge density maps have been calculated and analyzed. Lastly, optical properties of both binary and their related ternary alloys have been discussed in terms of the calculated dielectric function. The resultant optical parameters are compared with the available experimental data and other calculations. [Copyright &y& Elsevier]

Abstract: Density functional FP-LAPW+lo calculations have been performed to study the structural, electronic and magnetic properties of Mg1−x Mn x Te for compositional parameter x =0.25, 0.50, 0.75 and 1. Our calculations reveal the occurrence of ferromagnetism in these compounds in which the transition-metal atom is ordered in a periodical way thereby interacting directly with the host atoms. Results extracted from electronic band structure and density of states (DOS) of these alloys show the existence of direct energy band gap for both majority- and minority-spin cases, while the total energy calculations confirm the stability of ferromagnetic state as compared to anti-ferromagnetic state. The total magnetic moment for Mg1−x Mn x Te for each composition is found to be approximately 5μB, which indicates that the addition of Mn content does not affect the hole carrier concentration of the perfect MgTe compound. Moreover, the s–d exchange constant (N 0 α) and p–d exchange constant (N 0 β) are also calculated which are in accordance with a typical magneto-optical experiment. The estimated spin-exchange splitting energies originated by Mn 3d states energies, i.e. Δ X (s–d) and Δ X (p–d), show that the effective potential for minority-spin is more attractive than that of the majority-spin. Also, the p–d hybridization is found to cause the reduction of local magnetic moment of Mn and produce small local magnetic moments on the nonmagnetic Mg and Te sites. [Copyright &y& Elsevier]

Abstract: We report a systematic study of the structural, electronic and magnetic properties of Cr-doped CdTe for various Cr concentrations x (=0.25, 0.5, 0.75 and 1.0) using first principles calculations based on the density functional theory (DFT). The electronic band structure of the alloy has been calculated using the Wu–Cohen (WC) as well as the Angel-Vosko (EV) generalized gradient approximation (GGA) for the exchange-correlation potential. The analysis of the density of states (DOS) curves shows the half-metallic ferromagnetic character with half-metallic gap more than 0.52eV. While the origin of half-metallic ferromagnetism is explained, the band structure calculations are used to determine s (p)–d exchange constants N 0 α (conduction band) and N 0 β (valence band) that agree with typical magneto-optical experiment. It is found that the p–d hybridization reduces the magnetic moment of Cr from its free space charge value and produces small magnetic moments on the Cd and Te sites. Lastly, we discuss the robustness of half-metallicity with respect to the variation of lattice constants of the Cr x Cd1−x Te alloys. [Copyright &y& Elsevier]

Abstract: Structural, electronic and optical properties of ternary alloy system Cd x Zn1−x S have been studied using first-principles approach based on density functional theory. Electronic structure, density of states and energy band gap values for Cd x Zn1−x S are estimated in the range 0≤ x ≤1 using both the standard local density approximation (LDA) as well as the generalized gradient approximations (GGA) of Wu–Cohen (WC) for the exchange-correlation potential. It is observed that the direct band gap of Cd x Zn1−x S decreases nonlinearly with the compositional parameter x, as observed experimentally. It is also found that Cd s and d, S p and Zn d states play a major role in determining the electronic properties of this alloy system. Furthermore, results for complex dielectric constant ɛ(ω), refractive index n(ω), normal-incidence reflectivity R(ω), absorption coefficient α(ω) and optical conductivity σ(ω) are also described in a wide range of the incident photon energy and compared with the existing experimental data. [ABSTRACT FROM AUTHOR]

Double perovskite halides (DPHs) hold great promise for applications in energy conversion. This article provides a comprehensive exploration of the elastic, thermoelectric and optoelectronic characteristics of Cs 2 YCuX 6 (X = Cl, Br, I) DPHs. The examined DPHs indicate low thermal conductivity scales and high Seebeck coefficient significantly increased the figure of merit (ZT). The examined ZT∼1 at room temperature against temperature and chemical potential makes them appropriate for thermoelectric devices. [Display omitted] Double perovskite halides (DPHs) hold great promise for applications in energy conversion. This article provides a comprehensive exploration of the elastic, thermoelectric and optoelectronic characteristics of Cs 2 YCuX 6 (X = Cl, Br, I) DPHs. The elastic constants and phonon dispersion curves reveal ductile nature and mechanical and thermodynamic stability of the examined materials. The Born stability criteria ensures structural stability, while the formation energy ranging from −2.28 to −1.68 eV signifies thermodynamic viability. Furthermore, the thermodynamic stability of investigated double perovskites Cu 2 YCuX 6 (X = Cl, Br, I) have been verified by performing ab-initio finite temperature molecular dynamics (MD) simulation. The examination of mechanical characteristics affirms the ductile nature of the material, and its substantial anisotropic factor enhance its significance for device fabrication. The band gaps calculated at 2.65 eV, 2.55 eV, and 2.45 eV from band structures, highlight the significance of the studied double perovskites (DPs) for optoelectronic applications. Optical parameters yield information on minimal dispersion and expansive absorption band. Additionally, transport characteristics are analyzed through parameters such as Seebeck coefficient, thermal conductivity, electrical conductivity, and the Figure of merit (ZT). [ABSTRACT FROM AUTHOR]

[Display omitted] • Halide based double perovskites Na 2 AgTlZ 6 (Z = Cl, Br, I) have been explored for their optoelectronic and thermoelectric properties. • Lattice parameter, bulk modulus, and mechanical properties varied with substitution at halide side. • Study of optical, electronic and thermoelectric properties highlighted the importance of these materials for optoelectronic and thermoelectric applications. The bandgap engineering and deliberate band edge manipulation of perovskites make them potential candidates for the photovoltaic industry. Here we theoretically investigate the structure, density of states, and photovoltaic and thermoelectric characteristics of Na 2 AgTlZ 6 (Z = Cl, Br, I) using WIEN2k code. The incorporation of Br and I at the Cl site caused the increase in lattice constant which leads to the decrease in bulk modulus and Debye temperature. The computed values of Poisson (<0.26) and Pugh (<1.75) ratio verified their brittle nature. The bandgap analysis reveals direct bandgap nature and bandgap value lie in the visible region for parent composition and infrared and far infrared when Cl is replaced with Br and I. The density of state plots uncovers the shifting of energy states in valence and conduction bands towards the Fermi level with the increasing number of electrons in the halogens. The increase in the value of dielectric constant, refractive index, and shifting of peaks towards lower energy value is witnessed with atomic number of halogen atoms. The viability of these compositions for thermoelectric devices is further confirmed when electrical conductivity and Seebeck coefficient dependent Figure of merit and power factor are evaluated in the temperature range of 200–800 K. In addition, the anisotropic nature of studied compositions is explored through the computation of the modulus of elasticity including Young's modulus, Shear modulus in addition to compressibility, and Poisson's ratio. [ABSTRACT FROM AUTHOR]

To probe the applications in spintronics and sustainable energy devices of ZnMn 2 X 4 (X=S, Se, Te) spinels, their structural, elastic, electronic and thermoelectric properties have been studied in the present work. Structural properties reveal stability of ferromagnetic (FM) phase in these spinels which is further confirmed by computing the heat of formation for these compounds. The mechanical properties of the ZnMn 2 X 4 spinels have been investigated by computing their elastic constants, which show that all these spinels exhibit a brittle character. Moreover, electronic band structure and density of states reveal a half-metallic FM structure in all these spinels. Analysis of the band structure of these materials reveals a semiconducting nature in the spin down channel. Exchange constants (N 0 α and N 0 β) have been computed to directly probe the state splitting and our results large splitting of Mn 3d-states by N 0 β owing to its larger negative value as compared to N 0 α. The strong p-d hybridization is found to make exchange field dominant to crystal field which consequently induces ferromagnetism. In addition, the p-d hybridization reduces the magnetic moment of Mn ions by inducing traces of magnetic moments at non-magnetic sites. The observation of thermoelectric behavior within temperature range 200K–800K reveals positive Seeback coefficient indicating holes as majority charge carriers. Although the power factor is found to increase on going from ZnMn 2 S 4 to ZnMn 2 Te 4 , our results clearly show improvement of power factor with increasing temperature. Image 1 • Density functional theory calculations are performed for ZnMn 2 X 4 (X = S, Se, Te). • Structural analysis depict FM stability of ZnMn 2 X 4 (X = S, Se, Te). • The band structures analysis show their half-metallic nature of ZnMn 2 X 4 (X = S, Se, Te). • The computed magnetic parameters indicate potential spintronic devices applications. • The temperature effect on thermoelectric properties indicate that the material can be used even at elevated temperatures. [ABSTRACT FROM AUTHOR]

• Double perovskites halides K 2 AgBiX 6 (X = Cl, Br) are executed in terms of density functional theory. • Structural and thermodynamic investigation depict structural stability of K 2 AgBiX 6 in cubic phase. • The electronic band structures and optical analysis show both halides are strong candidate for the fabrication of solar cell devices. • Calculated thermoelectric parameters indicate that the both halides can be used even at elevated temperatures. Lead-free double-perovskites (DPs) K 2 AgBiX 6 (X = Cl, Br) has been executed as well as examined by ab-initio computations for solar cell energy sources. Improved and latest Becke and Johnson potential (TB-mBJ) has been suggested to calculate optoelectronics characteristics. The lattice constants reported theoretical and computed values using Perdew-Burke-Ernzerhof's generalized-gradient-approximation (PBEsol-GGA) had been determined in good agreement. The calculated bandgap 2.3 eV (K 2 AgBiCl 6) and 1.5 eV (K 2 AgBiBr 6) disclosed their indirect nature, which showed that these are suitable potential candidates for visible light solar-cell (SC). Optical ranges explain the dielectric-constant, light absorption and reflection, and refractive index. The maximum absorption band has been noted within the wavelength of 620–310 nm. In addition, the BoltzTraP (BT) Code has been determined thermoelectric characteristics that result in higher value Seebeck coefficient and lower thermal conductivity. Hence, executed theoretical calculation proposed that examined material has potential application in renewable energy fields. [ABSTRACT FROM AUTHOR]

Intense research has been done to build materials that are potential candidates for energy storage applications. Spinels are of great interest in this respect because they have vast potential to be used in Mg-based batteries. To explore their energy storage as well as transport response, we calculate Mg-based spinels, namely MgLu 2 Z 4 (Z S, Se). The full potential linearized augmented plane wave method has been used to examine their optoelectronic and transport response. An increase in the lattice constant has been observed by replacing S with Se, and our calculated values are in good agreement with those obtained experimentally. The Tran-Blaha modified Becke-Johnson exchange potential (TB-mBJ), has been used to study the optoelectronic and thermoelectric characteristics of the respective spinels. The dependence of these properties on the bandgap has also been observed. Replacing S with Se resulted in the transformation of the electronic bandgap from near-infrared to the visible region (MgLu 2 S 4 : 2.60 eV and MgLu 2 Se 4 : 2.00 eV). These results showed that these materials have the potential to be used in optoelectronic devices. The optical properties are discussed as a function of energy. Besides, the thermal transports are discussed with the help of Seebeck coefficient and figure of merit as a function of chemical potential and temperature. [ABSTRACT FROM AUTHOR]

• Density functional theory calculations under varying pressure are performed for ZnZrO 3. • Structural and elastic properties depict stability of ZnZrO 3. • A shift from indirect to direct band gap is observed due to employed pressure. • The computed optical parameters indicate potential opto-electronic devices applications. • The temperature effect on thermoelectric properties indicate that the material can be used even at elevated temperatures. The zinc zirconate ZnZrO 3 perovskite have been studied with respect to their physical properties by inducing pressure upto20 GPa. The predicted value of lattice constant for ZnZrO 3 determined using PBEsol-GGA is reasonable agreement with experimental value. Our calculations showed that Born mechanical stability criteria, confirmed the mechanical stability in cubic phase. Further, through Poisson and Pugh's ratios critical limits, the findings of the ductile strength have been computed. To explore the pressure induced band structure modification, a varying external pressure from 0 GPa to 20 GPa has been applied with a step size of 5 GPa. The change in band structure significantly affected the optical properties of the material under study. It was observed that the band gap of ZnZrO 3 shifted from indirect to direct at applied pressure of 15 GPa. The effect of this shifting on the dielectric constant, optical loss factor, reflection, refraction and absorption has been carried out in this work. To probe the potential of this composition for thermoelectric applications, its electrical conductivity, thermal conductivity, See-beck coefficient and power factor were also calculated. [ABSTRACT FROM AUTHOR]

The simultaneous existence of magnetic order and semiconducting nature in ferromagnetic semiconductors fascinate the spintronics technology to enhance the quantum computing and spin transistors. Therefore, electrons spin dependent ferromagnetism and thermoelectric properties of MgCr 2 X 4 (X ​= ​S, Se) spinels are scrutinized by density functional theory (DFT) based Wien2k code. The negative formation energy ensures thermodynamic stability. The band structures (BS) and density of states (DOS) ensure the ferromagnetic semiconductors nature of the studied spinel's. The insulating behavior in down spin and magnetic moment (Integer value) is the response of 100% spin polarization. The fulfillment of the condition Δ (d) > (Δ C F) and negative Δ (p d) have showed the dominant role of electrons spin to induce ferromagnetism. Moreover, influence of electrons spin on thermodynamic and thermoelectric characteristics are explored by specific heat capacity (C v), electrical conductivity (σ/τ), thermal conductivity ((κ/τ)), Seebeck coefficient (S) and power factor (σS2) by classical Boltzmann transport theory. The Ferromagnetic Semiconducting behavior of MgCr 2 X 4 (X ​= ​S, Se) in which up spin channel is semiconducting and down spin channel is insulating. Image 1 • The MgCr 2 X 4 (X ​= ​S, Se) spinels are ferromagnetic semiconductors with 100% spin polarization. • The exchange energies are exactly according to double exchange mechanism. • The above room temperature ferromagnetism enhance the potential for spintronics. • The thermal conductivity and electrical conductivity ratio is of the order of 10−5. [ABSTRACT FROM AUTHOR]

• Ab-initio studies to explore physical aspects of Lanthanide-based perovskites LaYO 3 (Y = Cr and Mn). • The studied perovskites tend to be stable along with ferromagnetic state. • The band structure analysis of LaCrO 3 perovskite revealed that LaMnO 3 exhibit half-metallic nature. • Study of thermoelectric properties show that both perovskites are ideal for thermoelectric device applications. Here, we report the ab-initio studies to explore physical aspects of Lanthanide-based perovskites LaYO 3 (Y = Cr and Mn), using full-potential linearized augmented plane waves logic. The calculated values of lattice constants were 3.91 Å and 3.86 Å for LaCrO 3 and LaMnO 3 respectively with PBEsol-GGA, comparable with available experimental data. Band structure and density of states played pivotal role in determination of the electronic properties. Figuring the exchange splitting energies (Δ x (d) and Δ x (pd)), crystal field energy (Δ CF) and Jahn-Teller energy (Δ JT) traverse the ferromagnetic semiconducting nature of studied La-perovskites. In addition, BoltzTraP code implemented to interrogate the thermoelectric properties. [ABSTRACT FROM AUTHOR]

• DFT calculations are executed for halides double perovskites Cs 2 ScAgX 6 (X = I, Cl, Br). • Structural and elastic investigations represent stability of Cs 2 ScAgX 6 (X = I, Cl, Br) in cubic phase. • The band structures analysis show their indirect bandgap nature of Cs 2 ScAgX 6 (X = I, Cl, Br). • The computed band structures and optical parameters indicate potential solar cells devices applications. • Electronic thermal coefficients are probed and suggested studied halides as promising thermoelectric materials. As a possible suitor for application of solar cells and thermoelectric, halide based double perovskites has been developed due to their ecosystem stability, non-toxicity and noticeable performance. In current study, we have explored structural stability and elastic properties of Cs 2 ScAgX 6 (X = I, Cl, Br) in the cubic phase through tolerance factor and Born stability criteria calculations. Further, we present an extensive analysis of optical, electronic and electronic transport characteristics. An indirect semiconducting bandgap in the range of 1.9 eV and 1.55 eV is observed while analyzing electronic band structure and play vital role in solar cells applications. According to their bandgap values, maximal absorption in visible region is perceived, which reduces the bandgap when chlorine is substituted with bromine and iodine. Dielectric constants and other relevant parameters were produced by studying optical characteristics of Cs 2 ScAgX 6. Within the visible region, the maximum absorption of light has been recorded by investigating dielectric constant. Finally, thermoelectric properties are computed using the BoltzTraP package. The value of figure of merit, which is around 0.74 at 300 K, clearly suggests that these materials are also used as potential candidate for thermoelectric devices. [ABSTRACT FROM AUTHOR]

The toxicity and instability of lead-based perovskites have been replaced with newly investigated stable lead-free inorganic perovskites. The current study included the comprehensive analysis of electronic behavior, elastic, optical, and transport characteristics of lead-free inorganic double perovskites (DPs) Rb 2 KTlX 6 (X = Cl, Br) halides for possible uses. These physical characteristics were revealed using density functional theory (DFT) based Wien2k code. Using the energy optimization process, we have computed structural parameters comparable to existing data using generalized gradient approximation (PBEsol-GGA). In addition, the elastic parameters, formation energy (−1.94 eV and −1.39 eV), and tolerance factor (0.98 and 0.97) endorsed the cubic stability of both halides. Further, we employed modified Becke-Johnson (mBJ) potential to an accurate value of direct bandgaps of both halides reveal that changing the anions from Cl to Br leads to significant adjustment in the band gap, transitioning from the visible to the IR spectrum, with energy levels ranging from 2.08 to 1.2 eV. Our calculated results of optical parameters indicate that both halides with remarkable optoelectronic working due to low reflectivity, high optical absorption, and conductivity. The study reveals that electronic transport factors are associated with temperature due to small bandgap of the materials. The observed figure of merit near unity indicates the semiconducting behavior of these materials that can be useful in thermoelectric tools. • First-principle calculations of DPs Rb 2 KTlX 6 (X = Cl, Br). • Direct bandgap semiconductor. • Optical characteristics for optoelectronic devices. • Transport characteristics are discussed in details for thermoelectric devices. [ABSTRACT FROM AUTHOR]

Intense research work is underway for identifying materials with potential applications in energy storage and energy harvesting systems. The magnesium based scandium chalcogenides have recently emerged as potential candidates for Mg batteries owing to their high Mg ionic conductivity and low electron conduction. At the same time, their band gaps are capable of absorbing electromagnetic radiations in visible to UV range; making them suitable for solar cell applications. In order to analyze the application of MgSc 2 X 4 (X = S, Se) compounds in energy devices, in this work we employ density functional theory calculations using the full potential linear augmented plane-wave method for examining their optoelectronic and thermoelectric properties. For the structural properties, the generalized gradient approximation functional designed for solids (PBEsol-GGA) has been used, while modified Becke and Johnson (mBJ) potential functional is used for computing the optoelectronic and transport properties. Our calculated optical properties indicate that these materials can find applications in solar cells. Moreover, the electronic transport properties computed using Boltzmann transport equation suggest carrier concentrations in MgSc 2 S 4 to MgSc 2 Se 4 spinels can be tuned for making them suitable for metal ion batteries. [ABSTRACT FROM AUTHOR]

Using the full-potential linearized augmented plane wave plus local orbitals method within the frame work of density functional theory, the Sc-based double halide perovskites K 2 ScAgZ 6 (Z = Cl, Br, I) are investigated for determining their physical properties. To investigate the structural and thermodynamic stability of these Sc-based double halide perovskites we calculate tolerance factor, formation energy, and phonon dispersion curve using GGA-PBEsol approximation. The calculated values of lattice parameters using GGA-PBEsol are found to be consistent with the available data. Subsequently, the Tran-Blaha modified Becke-Johnson (mBJ-LDA) potential is used for electronic properties. Implementation of TB-mBJ potential is clearly shows that K 2 ScAgZ 6 have indirect bandgap, which is consistent with the literature. To evaluate these double perovskites and reveal their potential use in optical devices, several optical parameters are computed for an incident photon energy range of 0–8 eV. The BoltzTraP code is also employed to investigate temperature dependent electrical characteristic of these compounds in the temperature range of 200–600 K. Investigated halide double-perovskites have been shown to display excellent physical properties for solar cells and renewable energy device applications. • In the cubic phase double perovskites are structurally and thermodynamically stable. • The calculated indirect bandgaps for K 2 ScAgCl 6 , K 2 ScAgBr 6 , and K 2 ScAgI 6 are 2.0, 1.85, and 1.65 eV. • These are suitable materials for solar cell devices due to their greatest least reflection, absorption, and optical loss in the visible area. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the structural, elastic, electronic and magnetic properties of Be 0.75 Co 0.25 Y (Y S, Se and Te) alloys, in their zinc-blend phase. This study is carried out by using the full-potential augmented plane wave plus local orbitals method within the density functional theory. Foe computing the exchange-correlation potential, the Wu and Cohen generalized gradient approximation is employed to calculate structural and elastic properties whereas the modified Becke and Johnson potential local density approximation is utilized to examine electronic and magnetic properties. By minimizing the total energy in paramagnetic (PM) and ferromagnetic (FM) phases, it is found the studied compounds are stable in FM structure. The mechanical behavior of the studied compounds is reported with the calculation of shear modulus, Young's modulus, and Poisson's ratio provides. Such mechanical aspects might be useful for the experimentalists to study the mechanical properties upon alloying BeY compounds with Co. We also compute electronic structures, density of states (total and partial), pd -exchange splitting and magnetic moments. Moreover, bond nature is studied by estimating the spin polarized charge densities of Be 0.75 Co 0.25 Y (Y S, Se and Te). [ABSTRACT FROM AUTHOR]

Lead free double perovkistes is an emerging class of optoelectronic material which have a huge potential for futuristic electronic industry. In present communication, we theoretically studied the structural, optoelectronic, and thermoelectric properties of Li 2 AgTlCl 6 and Li 2 AgTlBr 6 using WIEN2k software. The permissible values of tolerance factor and enthalpy of formation ensure the structural and thermodynamic stability of these compositions. The substitution of halides increase the lattice constant from 10.52 to 11.11 Å and reduce the bulk modulus from 33.38 to 26.20 GPa. The calculation of Poisons and Pugh ratios ensures their ductile nature, whereas the examination of band structure indicates exposed the bansgap value of 2.0 and 1.2 eV for Li 2 AgTlCl 6 and Li 2 AgTlBr 6 , respectively. A remarkable increase in optical parameters like static dielectric constant, refractive index, and shifting of peaks towards lower energy values is observed the replacement of Cl with Br. This substitution increased the electrical conductivity, specific heat at constant volume, Seebeck coefficient, and figure of merit that showed the feasibility of these compositions for photovoltaic and thermoelectric applications. [ABSTRACT FROM AUTHOR]

Abstract: For investigating the structural, electronic and magnetic properties of zincblende (ZB) Cd1−x V x Te (0≤x≤1), we have employed the Wu–Cohen generalized gradient approximation (WC-GGA) and the modified Becke and Johnson local density approximation (mBJLDA) functionals within the frame-work of spin polarized density functional theory (DFT). The former exchange-correlation parameterization scheme has been used for optimizing the equilibrium structural properties, while the electronic band structures, electron density of states (DOS) and charge densities are computed using both functionals and their performances are compared. Our results show that the electron spin polarization in unfilled V-3d orbitals gives rise to spin exchange splittings (Δ x (d) and Δ x (pd)) which is the cause of half metallic (HM) ferromagnetism in the V-doped CdTe as revealed by the computed DOS. Consequently, the nature of effective potential is more attractive in spin-down case rather than that in spin-up case. The total magnetic moment for each of the compounds under study is 3μB where the main contribution comes from the V atom, while the nonmagnetic sites Cd and Te are also bestowed with minor atomic magnetic moments due to Te-5p–V-3d hybridization. Furthermore, we calculated the exchange constants N 0 α and N 0 β to determine the conduction and valence band contributions in exchange splitting process. A comparison of the two functionals, considered in this work, shows that the mBJLDA provides a better description of the electronic structure especially of the ferromagnetic Cd1−x V x Te (0.75≤x≤1). Moreover, as compared to WC-GGA, the mBJLDA predicts high Curie temperatures in V-doped CdTe by providing significantly larger values of Δ x (d), Δ x (pd), N 0 α, N 0 β and, importantly, a quite wide HM gap. [Copyright &y& Elsevier]

• Rb 2 YInX 6 (X = Cl, Br, I) double perovskites have highly structural stability determined from volume-energy optimization and negative formation energy. • Direct bandgap in the range of 3.05–2.20 eV make them more attractive materials. • The Rb 2 YInBr 6 have large value of figure of merit which means it has largest conversion efficiency to convert thermal energy into electrical energy. The double perovskite-based materials have attracted considerable attention of scientists owing to their potential applications in optoelectronic and transport properties. Here, we report the optoelectronic and transport properties of Rb 2 YInX 6 (X = Cl, Br, I) double perovskites by DFT computations. By computing tolerance factor (t G) , enthalpy of formation (ΔH f) and lattice constant (a o), the thermodynamic and structural stabilities are verified. The energy bandgap computations for Rb 2 YInX 6 gives direct bandgap having values 3.05, 2.60 and 2.20 eV for Cl, Br and I based compositions respectively. Optical absorption calculations executed within the energy range of 2–8 eV which validate its use in optoelectronic applications like solar cells. Using semi classical Boltzmann theory computed values of ZT illustrates that Rb 2 YInBr 6 is fairly good candidate for transport applications. These compounds may attain consideration in optoelectronic and thermoelectric properties. [ABSTRACT FROM AUTHOR]

Abstract: We systematically explore Cr-doped zinc blende BeSe and BeTe compounds in terms of their structural, electronic and magnetic properties by using the first-principles full-potential linearized augmented plane waves plus local orbitals (FP-LAPW + lo) method. The state stability of the doped materials has been studied by calculating the heat of formation and analysing minimum total energies in ferromagnetic (FM) and anti-ferromagnetic (AFM) coupling. A non linear dependency of Cr concentration on the lattice parameters and bulk modulus is found which shows small deviation from Vegard''s law. Our calculations for each Cr concentration were performed using two different density functional theory functionals which are the Wu and Cohen (WC) and the modified Becke and Johnson local (spin) density approximation (mBJLDA). The functionals generate spin dependent band structures, electronic density of state (DOS) and magnetic moments that exhibit occurrence of half-metallic ferromagnetism which is caused by spin polarization of electron in Cr-d orbitals. Importantly, comparison between the two functionals shows that the mBJLDA functional provides a better description of the electronic structure of the Cr-doped binary systems. The calculated exchange interaction and exchange constant, N 0 α and N 0 β, respectively, are consistent with the values from typical magneto-optical experiment and conversely, the calculated charge spin densities allowed us to understand the bonding nature. In addition, the calculations of spin exchange splitting, Δ x (d), exhibit important indication regarding the attractive effective potential for minority spin rather than majority spin. [Copyright &y& Elsevier]

• The structural, electronic, and optical features of Cu 2 ZnSn(S x Te 1-x) 4 alloys are examined. • Kesterite structure is more favorable and sustainable for these materials than stannite one. • Absorption coefficient spectra are altered with the change of Te composition in these systems. • A birefringence occurred in Cu 2 ZnSn(S x Te 1-x) 4 alloys with the variation of composition x. • CZTS and CZTS 0.75 Te 0.25 could be promising materials as absorber layers of thin film solar cells. Cu 2 ZnSnS 4 (CZTS), a quaternary material formed of Earth-abundant elements, is promising in thin-film solar cell devices, as absorbing layer. The high efficiency of solar energy conversion (>12%) recorded in chalcogen-doped Cu 2 ZnSnS 4 renders it an attractive material for the analysis of the structural stability, electronic band structures, and optical characteristics of Cu 2 ZnSn(S x Te 1-x) 4 alloys (0 ≤ x ≤ 1) by first-principles calculations. By employing full-potential linearized augmented plane-wave (FP-LAPW) methodology, the acquired results indicate that CZTS and Cu 2 ZnSnTe 4 (CZTTe) parent compounds possess wide and narrow direct band gaps, respectively. The optical characteristics of Cu 2 ZnSn(S x Te 1-x) 4 alloys and their bulk counterparts were computed in terms of the complex dielectric function, which allows the examination of the optical absorption, reflectivity, and refractive index of these ultimate alloys. It is inferred that the S/Te compositional ratio in Cu 2 ZnSn(S x Te 1-x) 4 has a significant influence on the optical absorption of electromagnetic radiation in the visible to the infrared (IR) regimes. Our results indicate that the increase of Te concentration leads to a red shift of the major feature peaks in the optical absorption spectra. Because of their direct band gap and remarkable optical absorption, Cu 2 ZnSn(S x Te 1-x) 4 alloys with S/Te compositional ratios under 0.5 could be useful materials in thin-film solar cell devices, as absorbing layers. This theoretical report is expected to provide relevant information for future experimental works involving the design of novel solar cell materials based on CZTST systems. [ABSTRACT FROM AUTHOR]

Calculated Debye temperature (θ D), average sound velocity (υ m), melting temperature (Tm) for RbXO 2 (X = Al, Ga, In) oxides. • The optoelectronic and thermoelectric properties of RbXO 2 (X = Al, Ga, In) oxides have been investigated. • The structural stability of RbXO 2 oxides has been confirmed from Goldschmidt's tolerance factor. • The direct bandgap nature of the RbXO 2 oxides is observed. • The thermal efficiency increases from Al to In, because bandgap decreases that increases the electrical conductivity. The optoelectronic and thermoelectric properties of RbXO 2 (X = Al, Ga, In) oxides have been investigated by using the density functional theory (DFT). The stability of RbXO 2 has been confirmed from the negative value of enthalpy of formation, Goldschmidt's tolerance factor (0.91, 0.95 and 1.02) and Born mechanical stability criteria. The bandgap of the studied RbXO 2 lies in the range from 3.3 eV to 1.25 eV, which shifts the optical region from near ultraviolet to near infrared region of spectrum. The comparative analysis of optical and thermoelectric properties shows RbXO 2 are more suitable for optoelectronic applications than thermoelectric applications. [ABSTRACT FROM AUTHOR]

Abstract The structural behavior of MgIn 2 X 4 (X = S, Se) has been elaborated by FP-LAPW + lo method as included in the Wien2k code. The stability of the phase has been confirmed by negative formation energy (−1.24 eV for MgIn 2 S 4 and -0.78 eV for MgIn 2 Se 4). The band gap dependent opto-electronic and thermoelectric properties are realized by modified Becke-Johnson exchange potential. The electronic band gap tuned from ultraviolet to visible (3.1 eV and 1.9 eV) by replacing the S with Se that motivated the studied spinels for photovoltaic and solar applications. Moreover, the attenuation of light, dispersion, transparency, reflection and energy loss when light scattered from material are discussed as function of energy. The thermal conductivity to electrical conductivity ratio, potential gradient and thermal efficiency in the range 0.78–0.80 are elaborated. The comparative study of opto-electronic and thermoelectric properties for energy harvesting increases the potential for optoelectronic than thermoelectric applications. Graphical abstract The Figure of merit (ZT) values of MgIn 2 X 4 (X = S, Se) spinels against (a) chemical potential and (b) temperature. Image 1 Highlights • The study of structural behavior of MgIn 2 X 4 (X = S, Se) by using DFT. • The investigation of band gap dependent opto-electronic and thermoelectric properties. • The band gap tuning from ultraviolet to visible by changing anion. • The high value of thermal efficiency increases importance for thermoelectric applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Halide based double perovskites K 2 ScAuX 6 (X = Br, I) have been theoretically investigated using WEIN2k software. • Structural parameters were optimized using Perdew–Burke–Ernzerhof generized gradient approximation (PBEsol-GGA) • Investgation of mechanical response of these materials revealed their ductile nature. • Indirect band gap nature with bang gap values of 2.20 eV and 1.90 eV were estimated using mBJ potential. • Electronic transport properties in a wide range of temperature has been evaluated. Here we report a theoretical analysis of various technologically important physical properties of double perovskites K 2 ScAuX 6 (X = Cl, Br) including thansport, optoelecronic, and strucutral. The computation of tolerance factor and estimation of entahly of formation remained key indicators to ensure the srucutal and thermodynamic stability of these compositions. The substitution of Br at Cl site increased the lattice parameter and reduced the bulk modulus. The computation of elastic constants-based modulus of elasticity revealed their ductile nature. The analysis of electronic band structure unveiled their indirect bandgap nature. Polarizability of material is accessed by computing the dielectric constant, scattering by extinction coefficient, absorption by refractive index, in addition to electrical and thermal conductivity and the Seebeck coefficient, highlighted their suitability for advanced technologically important applications in optoelectronic and thermoelectric industry. [ABSTRACT FROM AUTHOR]

Owing to the large energy storage capacity and higher working voltage, the spinel oxides LiV 2 O 4 and LiCr 2 O 4 , have remained under intense research attention for utilization as electrode materials in lithium-ion batteries. In this study, we explore the half-metallic nature and thermoelectric response in both LiV 2 O 4 and LiCr 2 O 4 spinel oxides using ab-initio density functional theory (DFT) based computations. The ground-state energies of these compounds have been studied at the optimized structural parameters in the ferromagnetic phase. In order to obtain a correct picture of the electronic structure and magnetic properties, the modified Becke-Johnson (mBJ) potential is applied to compute the electronic structures. The half-metallic behavior is confirmed by the spin-polarized electronic band structures and density of state plots. The magnetic nature is elucidated by computing the John-Teller energy, direct and indirect exchange and crystal field splitting energies. Our computations indicate strong hybridization decreasing the V/Cr site magnetic moments and increasing magnetic momenta at the nonmagnetic atomic sites. We also present the computed parameters significant for expressing the thermoelectric response, which are electrical conductivity, thermal conductivity, See-beck coefficient and power factor. The computed properties are of immense interest owing to the potential spintronics and Li-ion battery applications of the studied spinel materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Halide based double perovskites K 2 YAgX 6 (X = Br, I) have been theoretically investigated using WEIN2k software. • Structural parameters were optimized using the Perdew–Burke–Ernzerhof generized gradient approximation (PBEsol-GGA) • Investgation of the mechanical response of these materials revealed their ductile nature. • An indirect band gap nature with bang gap values of 3.4 and 2.6 eV were estimated using mBJ potential. • Electronic transport properties over a wide range of temperatures have been evaluated. The halide based double perovskites K 2 YAgBr 6 and K 2 YAgI 6 have been extensively investigated for their optoelectronic properties using the full-potential linearized augmented plane wave method. Their thermodynamic and structural stabilities were mapped by computing the enthalpy of formation and tolerance factor respectively, which revealed that K 2 YAgBr 6 is more stable. The computed values of the structural parameters in the ground state showed that the unit cell expands upon replacement of Br with I, which is explained based on their relative ionic radii. The Poisson and Pugh ratio were calculated, based on the elastic constants, which argued the ductile nature of these double perovskites. The presence of band edges at two different symmetry points proclaimed their indirect bandgap nature and the bandgap value decreases upon replacement of Br with I. The computation of optical parameters manifested an increasing trend in the dielectric constant, refractive index and reflectivity when Br is substituted with I. Semi-classical Boltzmann theory-based BoltzTraP code is employed to estimate different thermoelectric parameters, including the power factor and figure of merit, which exhibited the potential of these materials for optoelectronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

In this study, we have employed first-principle calculations to investigate the structural, mechanical, electronic, magnetic and the optical properties of Co-doped ZnS and ZnSe compounds. The ferromagnetic structural stability is determined from the calculated total energy difference between ferromagnetic and antiferromagnetic phases. The calculated mechanical properties show that these materials are mechanically stable, ductile and anisotropic. The modified Becke-Johnson local density approximation functional is used for accurate prediction of the electronic properties of Co-doped ZnS and ZnSe. The electronic band structures and density of states plots reveal ferromagnetic semiconducting behavior in these compounds, which is explained in terms of exchange and crystal field splitting energies, exchange constants and magnetic moments. The optical properties have been studied systematically by computing parameters like real and imaginary part of the dielectric constant, refractive index, extinction and absorption coefficients, optical conductivity, reflectivity and energy loss function. The tuning of band gap from ultraviolet to visible region with minimum optical loss, due to the Co doping, makes these materials suitable candidates for optoelectronic device fabrications. [ABSTRACT FROM AUTHOR]