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The electronic and optical properties of ternary-type chalcogenides are of great interest for solar energy conversion applications. In this study, we investigated the optical, electronic, and transport properties of Sr 2 GeX 4 (X = S and Se) materials using first-principles calculations based on density functional theory. We found that these materials have a robust covalent bond nature and substantial band gaps. The density of states calculations revealed that the Sr-s and Ge-s states play a predominant role, while the S-s and S-p states have a minor influence. The optical properties of the materials are anisotropic, and they have significant UV absorption. The positive Seebeck coefficient values suggest that holes are the primary charge carriers in both materials. The study also discussed various other crucial thermoelectric parameters, which collectively suggest the suitability of these materials for thermoelectric applications. Overall, this study provides valuable insights into the optoelectronic and thermoelectric properties of Sr 2 GeX 4 materials, which could significantly contribute to the development of efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

In the present study, we elaborated a group of SrXF 3 (i.e., SrNbF 3 , SrTiF 3 and SrZrF 3) fluoride materials using the computational approach and calculated their structural, electronic, thermal, mechanical, and optical properties with the help of WIEN2K. Amongst the three presently studied SrNbF 3 , SrTiF 3 and SrZrF 3 materials, the material with Nb at the X site showed the least value of energy at the ground state than the SrTiF 3 and SrZrF 3 materials. Furthermore, the SrNbF 3 material also showed superior value of bulk modulus which certifies its extensive opposition to the compressibility amidst the three studied materials. IRelast package is used to find the elastic constants from which mechanical stability and other mechanical parameters are calculated. Analysis of elastic properties reveals that all compounds have ductile nature. Temperature dependent thermoelectric properties such as Seebeck coefficient (S), electronic thermal conductivity (κe), and figure of merit (ZT) were calculated with Boltztrap. Our results revealed that among the investigated perovskites, SrTiF 3 exhibited ZT∼0.19 and suitable for thermoelectric applications at higher temperature. For optoelectronic response, the optical properties of the given compounds were calculated for the photon energy 0–20 eV. The response of the understudy compounds over a wide range of electromagnetic radiations, indicating their potential usage for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Various physical properties (electronic, optical and thermoelectric) of cubic perovskite oxides Sr X O 3 (X = Sc, Ge, Si) are investigated by using the density functional theory (DFT) within Wien2K code. This code is based on different approximations such as generalized gradient approximation GGA, PBEsol, LDA, WC and the modified Becke–Johnson exchange potentials (mBJ, nmBJ and unmBJ). Structural properties and the optimization have been calculated using PBEsol functional which showed a significant results that are in good agreement with the experimental ones. The results for physical properties such as electronic, thermoelectric and optical are analyzed in detail by using the nmBJ approximation. The obtained results present an opening gap for SrSiO 3 , SrGeO 3 and a metallic behavior for SrScO 3. An average of transmittance which is about 94% to 97% was observed in the range of visible light. The increase of electrical conductivity with temperature confirms the effect of thermal agitation on the concentration of charges carriers using BolzTrap2 Package. Lastly a phonon dispersion was made and show that for X = Ge and Si, the structure is relatively stable while SrScO 3 is dynamically unstable. These results prove the ability that these materials can be exploited in many applications and manufacturing of optoelectronics for Sensors. [ABSTRACT FROM AUTHOR]

Study of fundamental physical properties of titanium dioxide (TiO 2 ) is crucial to determine its potential for different applications, such as study of electronic band gap energy is essential to exploit it for optoelectronics and solar cell technology. We present here investigations pertaining to structural, electronic and optical properties of rutile, anatase and brookite polymorphs of TiO 2 by employing state of the art full potential (FP) linearized (L) augmented plane wave plus local orbitals (APW+lo) approach realized in WIEN2k package and framed within density functional theory (DFT). To incorporate exchange correlation(XC) energy functional/potential part into total energy, these calculations were carried out at the level of PW–LDA, PBE–GGA, WC–GGA, EV–GGA, and mBJ–GGA which are exploited as the manipulated variables in this work. From our computations, the obtained structural parameters results were found to be consistent with the available experimental results. The analysis of electronic band gap structure calculations point to TiO 2 as a semiconducting material in all three phases, whereas band gap character around Fermi level was found to be indirect for anatase, and direct for rutile and brookite phases. Density of state (DOS) profiles showed a substantial degree of hybridation between O 2p and Ti 3d in conduction and valence band regions, illustrating a strong interaction between Ti and O atoms in TiO 2 compund. In addition, our investigations of the optical properties also endorse the interband transitions from O 2p in valence band to Ti 3d in conduction band. [ABSTRACT FROM AUTHOR]

The Iridium-based transition metal chalcogenides display significant results in terms of their optoelectronic and thermoelectric properties are investigated using the accurate Trans-Blaha modified Becke–Johnson potential under the framework of the density functional theory. The stable lattice constant was used to calculate the electronic band structures and density of states. Our calculated results show an indirect bandgap nature because conduction band minima and valance band maxima do not co-exist at the same Г-point symmetry. An increase in the bandgap value i.e., (IrSbS) > (IrSbSe) > (IrSbTe) can be attributed due to a shift linked with conduction bands near the Fermi energy level. The total and partial density of states for the three TMC's were computed, compared, and discussed in detail at different energy ranges. The frequency-dependent linear optical parameters such as the complex dielectric function absorption coefficient, extinction coefficient, reflectivity, refractive index, and the energy loss function are calculated and discussed. These computed results confirm that our studied materials are the most promising materials for optical devices that work in the infrared and visible regions of the solar spectrum. Additionally, the thermoelectric transport parameters like the Seebeck coefficient, thermal conductivity, specific heat capacity, the power factor, and the figure of merit were also computed by using the BoltzTrap code. The computed high specific heat capacity along with power factor value for IrSbTe as compared to the other two materials elucidate and confirm the material to be more efficient at generating or extracting heat energy. [ABSTRACT FROM AUTHOR]

Abstract: We present comparative calculations of the electronic structure of Cd and Zn based group II–VI compounds and their heterostructures based on the density functional and tight binding theories. The first principles density functional theory (DFT) uses the modified Becke–Johnson exchange potential with LDA correlation potential (MBJLDA) and the semi-empirical tight binding theory uses the first nearest neighbor (NN) and second nearest neighbor (2NN) basis with spin–orbit coupling of II cation (Cd, Zn) and VI anion (S, Se, Te) atoms for calculating the electronic structure of Cd and Zn based II–VI compounds and their heterostructures. The results of DFT with MBJLDA functional and NN and 2NN TB models are found to be in excellent agreement with measured band gaps of CdX and ZnX (X=S, Se, Te) based group II–VI compounds and their CdZnS/CdS, CdSTe/CdTe and ZnSSe/ZnSe heterostructures. We conclude that the NN TB model gives much more physical insight than the (2NN) TB model, making use of the fictitious s* state unnecessary. [Copyright &y& Elsevier]

An essential issue in electro-optical applications is to design materials with appropriate band gaps. In the framework of density functional theory (DFT), the generalized gradient approximation (GGA) and local density approximation (LDA) generally underestimate band gaps for semiconductors. Hybrid functionals that include some exact Hartree–Fock exchange are known to be better. In this research, we applied hybrid functionals, which has the main factor of providing almost accurate exchange potential, for calculating structural, electronic and optical properties of alkaline earth metal oxides. Results show that the hybrid functionals have a tendency to improve the description of structural and electronic parameters with respect to LDA and GGA. We find that the PBE0 and B3PW91 are the best functional for estimating lattice constant. LDA-HF gives the better results for calculating the energy band gaps with respect to the experimental values, and B3PW91 and PBE0 improved the amount of dielectric constant. The calculated imaginary part of dielectric function and reflectivity spectra shows that B3PW91 and LDA-Fock α give the best accordance with experimental results. The present work has shown that applying hybrid functionals can lead to very accurate results, describing correctly the structural, electronic and optical properties of the alkaline earth metal oxides. [ABSTRACT FROM AUTHOR]

In this work, we report a theoretical investigation of the structural, electronic and optical properties of Cd 1 − x Ag x S alloys with a wurtzite structure. The calculations were performed using the density functional theory (DFT). The full potential linearized augmented plane wave (FPLAPW) scheme, implemented in Wien2k package, was employed. The modified Becke–Johnson potential with generalized gradient approximation (mBJGGA), which combines the Becke–Johnson exchange potential with the generalized gradient approximation correlation potential, was used to evaluate the alloys band structure. The study was carried out for the composition of silver x = 0 , 0.027, and 0.055. The obtained band structures and the density of states of these alloys revel that by increasing the silver composition in CdS matrix, the Fermi level cross the E(k) curves in the majority-spin states showing a metallic behavior. While the minority-spin state is semiconducting. A band gap channel was observed between the spin up and spin down level giving rise to a half metallic behavior. The origin of this bandgap is attributed to the silver d-band hybridization. The optical properties were also investigated and were found to be deeply affected by the silver composition. The optical absorption is gradually shifted to the lower energy and the compound becomes more absorbent in the infrared region. The structural and optoelectronic proprieties of the half metal Ag-doped CdS materials, were investigated and are presented in the current study and discussed in details. The findings of the study show that Cd 1 − x Ag x S alloys with their spin-based properties could pave the way for many novel optoelectronic devices in addition to spintronics applications. [Display omitted] • A decrease in the lattice parameters occurs after the substitution of Cd with Ag atoms in the CdAgS supercell. • The density of states shows a strong hybridization of the d states of Ag and the p orbitals of S near the Fermi level. • A transition from semi-metal to metal character of CdAgS occurs by increasing the silver composition. • The peaks of the dielectric function imaginary part in the lower energy region move to the infrared spectrum with the silver composition. • The Ag-doped CdS alloys clearly show novel electronic properties for optoelectronic applications. [ABSTRACT FROM AUTHOR]

In the present work the electronic, optical, and dielectric properties of the orthorhombic crystal structure of OsP 2 semiconductor are investigated through first-principles calculations using the all-electron full-potential linearized augmented plane wave (FP-LAPW). All properties were calculated and discussed within the generalized gradient approximation (GGA) and the local density approximation (LDA), with and without the modified Becke-Johnson exchange-correlation potential (mBJ). The optimized structure parameters obtained by minimizing the total energy and electronic charge as part of the LDA were found to be in good agreement with existing experimental parameters. The calculation performed by the LDA with mBJ exchange-correlation potential confirms the indirect electronic transition located in the Γ-Z direction and gives a bandgap energy closer to the experimental value compared with GGA and GGA-mBJ results. The SOC underestimates the bandgap, and the splitting of the Os-5d states causes a band shift toward lower energies. In addition, GGA-mBJ and LDA-mBJ calculations demonstrate that the OsP 2 semiconductor exhibits an insignificant optical anisotropy character in the infrared region, with a high refractive index of approximately 1000 cm−1 (n = 3.95). [ABSTRACT FROM AUTHOR]