Opto-electronic and thermoelectric properties of MgIn2X4 (X = S, Se) spinels via ab-initio calculations.

The structural behavior of MgIn2X4 (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 MgIn2S4 and -0.78 eV for MgIn2Se4). 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.

Physical properties of cubic BaGeO3 perovskite at various pressure using first-principle calculations for energy renewable devices.

The electronic, optical and thermoelectric analyses of BaGeO3 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.

Systematic study of room-temperature ferromagnetism and the optical response of Zn1-x TM x S/Se (TM = Mn, Fe, Co, Ni) ferromagnets: first-principle approach.

The structural, magnetic and optical characteristics of Zn1-x TM x S/Se (TM = Mn, Fe, Co, Ni and x = 6.25%) have been investigated through the full-potential linearized augmented plane wave method within the framework of density functional theory. The optimized structures have been used to calculate the ferromagnetic and the antiferromagnetic ground-state energies. The stability of the ferromagnetic phase has been confirmed from the formation and the cohesive energies. The Heisenberg model is used to elucidate the Curie temperature (T c) of these alloys. From the band structures and density of states plots, it has been observed that TM-doped ZnS/Se alloys appear to be semiconductors and exhibit ferromagnetism. In addition, the observed ferromagnetism has also been explained in terms of direct exchange energy Δ x (d), exchange splitting energy Δ x (pd), crystal-field energy (E crys), exchange constants (N 0 α and N 0 ß) and magnetic moments that shows potential spintronic applications. The optical behaviors of these alloys have been explained in terms of real and imaginary parts of the dielectric constant ε(ω), refractive index n(ω), extinction coefficient K(ω), reflectivity R(ω) and absorption coefficient σ(ω), in the energy range 0-25 eV. The calculated static limits of the band gaps and real part of the dielectric constants satisfy the Penn model. The critical limits of the imaginary part of the dielectric constants and absorption coefficients indicate that these alloys can be operated in the visible and the ultraviolet region of the electromagnetic spectrum; therefore, make them important for optoelectronic applications.