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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]

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]

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]

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]

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]

• 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]

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]

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]

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]

Ab-initio calculations for V-doped BeSe and BeTe semiconductors are performed by means of all-electrons full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. The structural properties are optimized using the Wu-Cohen generalized gradient approximation functional, whereas modified Becke and Jhonson local density approximation functional has been employed for evaluating the spin-polarized electronic and magnetic properties. Magnetic stability at various doping concentrations in ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering is investigated by comparing the minimum total energies and enthalpies of formation (Δ H ). Studied band structures, density of states, total energy, exchange interactions and magnetic moments manifest both alloys with half-metallic ferromagnetic behavior. Moreover, their valance bands are found to be paired ferromagnetically with V atoms. Furthermore, it was observed that the magnetic moment of vanadium atom reduces from free space charge value due to p–d hybridization which yields small magnetic moments on the Be, Se and Te sites. [ABSTRACT FROM AUTHOR]

The mechanical, thermodynamic, electronic, and optical properties of Na 2 MoO 4 (NMO) and Na 2 WO 4 (NWO) spinels are elaborated by density functional theory (DFT) based full potential augmented plane wave method (FP-LAPW + lo). Our optimized lattice constants for the studied spinels are in good agreement with that obtained experimentally. The enthalpy of formation ensures the thermodynamic stability of NMO and NWO in the cubic phase. The Born mechanical stability criteria guarantees their mechanical stability, while Poisson ratio (ν) and Pugh's ratio (B/G) infer their brittle behavior. The Debye temperature (θ D) is significant for NMO than NWO. The wide bandgap of 3.5 eV for NMO and 4.4 eV for NWO show the maximum absorption in the ultraviolet region that increases their importance for optoelectronic applications. The optical properties are explained in term of dielectric constant, refractive index, absorption of light, reflection, and optical loss factor. [ABSTRACT FROM AUTHOR]