High-performance optoelectronic and thermoelectric properties of transparent conductors based on Tl2O3 under pressure.

In this work, the full-potential linearized augmented plane wave method (FP- LAPW) and the modified Becke-Johnson (mBJ) functional with spin-orbit (SO) coupling are used the obtain the structural, optoelectronic and thermoelectric properties of Tl2O3 under pressure. The results show that Tl2O3, as transparent conducting oxide (TCO), is a direct bandgap semiconductor with a band gap of 1.23 eV. The band gap value and the effective mass of electrons increases by increasing pressure. Density of state spectra reveal that the nature of electrons in Tl-6s state in the bottom of conduction band, like free electrons in s state, is responsible for the conducting behavior of Tl2O3. A blue shift is observed in optical spectra such as electron energy loss and absorption spectra with an increase in pressure. Obtained dielectric constants under pressure are inversely proportional to the band gap value according to Penn model. The effects of pressure on thermometric properties are also explored. The hydrostatic pressure increases Seebeck coefficient, while it decreases thermal conductivity that is an effective way to the enhancement of the thermoelectric efficiency of TCOs. A figure of merit (ZT) of 0.98 in p-type Tl2O3 is achieved that is desirable for using in thermoelectric devices.

Effects of the Hubbard potential on the NMR shielding and optoelectronic properties of BiMnVO5 compound.

This study explores the nuclear magnetic shielding, chemical shifts, and the optoelectronic properties of the BiMnVO5 compound using the full-potential linearized augmented plane wave method within the generalized gradient approximation by employing the Hubbard model (GGA + U). The 209Bi and 51V chemical shifts and bandgap values of the BiMnVO5 compound in a triclinic crystal structure are found to be directly related to Hubbard potential. The relationship between the isotropic nuclear magnetic shielding σiso and chemical shift δiso is obtained with a slope of 1.0231 and - 0.00188 for 209Bi and 51V atoms, respectively. It is also observed that the bandgap, isotropic nuclear magnetic shielding, and chemical shifts increase with the change in Hubbard potentials (U) of 3, 4, 5, 6, and 7.

DFT investigations of AgMC7H10N2 (M = Cl, Br, and I) metal organic molecules: NMR, optoelectronic, and transport properties.

The full-potential linearized augmented plane wave (FP-LAPW) method was used for the calculation of the structural, nuclear magnetic resonance (NMR), optoelectronic, and thermoelectric properties of AgMC7H10N2 (M = Cl, Br, and I) compounds. The calculated wide band gap of AgMC7H10N2 (M = Cl, Br, and I) metal organic molecules with the density of states approach were 3.32, 3.29, and 3.10 eV, respectively. The NMR parameters are calculated for the Ag, Cl, Br, I, C, N, O, and H elements. It is found that by decreasing bandgap, the isotropic NMR chemical shielding values of Cl, Br, and I elements increase. The strong hybridization of Ag-4d, Cl-3p, Br-4p, and I-5p states are observed at the top of the valence band. The birefringence and anisotropic properties are observed in the optical spectra with high plasmon energies, and the figure of merit, ZT, of 0.98 for AgCl(C7H10N2) compound is found at 300 K. Hence, these compounds are attractive flexible metal organic molecules for optoelectronic and transport applications.

Investigation of 205 Tl NMR shielding, structural, and electronical properties in thallium halides by applying PBE-GGA, YS-PBE0 and mBJ functionals.

We report the structural, electronical, and heavy nuclear 205 Tl Nuclear Magnetic Resonance (NMR) shielding properties of thallium halides TlX (X = F, Cl, Br, and I) by the first principles calculation. The Perdew-Burke-Ernzerhof Generalized Gradient Approximation, Yukawa Screened-PBE0 hybrid functional, and modified Becke-Johnson (mBJ) functionals including the relativistic and spin-orbit coupling effects are applied for calculation of the exchange-correlation potentials. Calculated PDOS spectra display that the valence band is composed of the X-s, Tl-5d, X-p, and Tl-6s states, and these states play an important role in 205 Tl NMR shielding. Our findings indicate that the nuclear magnetic shielding parameters depend on the electronic properties. Obtained results by mBJ show that there is a close agreement between the experimental and the calculated NMR parameters.

Theoretical investigations of thermoelectric phenomena in binary semiconducting skutterudites.

In this study, we explored the thermoelectric properties of the host thermoelectric materials (TM), namely, binary skutterudites, using a combination of simulations based on density functional theory and post-DFT Boltzmann's semiclassical theory. The calculations were performed close to the Fermi surface for the Seebeck coefficient and other thermoelectric parameters. Our results demonstrated that CoSb3 exhibited the highest Seebeck value at room temperature among all the compounds (CoP3, CoAs3, CoSb3, IrP3, IrAs3, IrSb3, RhAs3, and RhSb3), which confirmed that this compound is an ideal host material for thermoelectric applications. Furthermore, the calculated electrical conductivity values show that RhAs3 has the largest value of 3.736 × 105 Ω-1 m-1. However, at high temperatures, the Seebeck values for all of these compounds are almost constant due to the activation of the minority charge carriers.