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The I2-II-IV-VI4 series of quaternary chalcogenides semiconductors have drawn wide interest for their potential application as solar-cell absorbers. In this paper, we present a study of electronic and optical properties of the equilibrium kesterite structure (KS) of Cu2ZnGeS4 (CZGS) calculated by means of the full potential linearized augmented plane wave method. For this purpose, we used the Wien2k code based on the density functional theory with the generalized gradient approximation (GGA), modified Becke-Johnson exchange potential (mBJ) and the Hubbard potential U. The TB-mBJ is used alone or combined with U (TB-mBJ, and TB-mBJ+U). The results are compared with other theoretical results and the available experimental ones. The obtained results show that the top of the valence band is mainly composed by the Cu d orbital while the bottom of the conduction band is a mixture of Ge s and S p states. It was found that KS-CZGS has a direct band gap of 0.3, 1.8 and 2.0 eV using GGA, GGA+TB-mBJ and GGA+TB-mBJ+U, respectively. It is observed that states exist above the Fermi level (0 eV) with a width of 0.3 and 0.2 eV when we use GGA and GGA+TB-mBJ, while these states come down under the Fermi level when using GGA+TB-mBJ+U. The optical properties are calculated and an almost isotropic behavior is found in contrast to the reported properties of the stannite phase. This behavior can be linked to the charge density and the structure. [ABSTRACT FROM AUTHOR]

First principle calculations have been performed to investigate the effect of hydrostatic pressure on the electronic structure and optical properties of the narrow band gap InAs compound. The calculations have been done by the full-potential linearized augmented plane wave method, based on the density functional theory utilizing Wien2k package. The exchange-correlation potential is treated by the generalized gradient approximation and a combination of modified Becke-Johnson plus local-density approximation functional. Regarding the electronic structure, using the band structure calculations at different pressures, the pressure dependence of band gap energy is calculated. In the case of optical properties, the effect of hydrostatic pressure on the real and imaginary parts of the dielectric function ε(ω) is calculated. [ABSTRACT FROM AUTHOR]

In this article, density functional theory has been used to investigate the structural and optoelectronic properties of PbZrO3 (PZO) under pressure from 0 to 350 GPa. In order to achieve ground state structural stability, generalized gradient approximations has been utilized. By studying electronic properties, indirect band-gap nature of PZO appears to change at 15 GPa to direct band-gap. Optical analysis include under pressure responses of real and imaginary parts of dielectric function, optical conductivity, optical absorption coefficient, energy loss function, refractive index, reflectivity and extinction coefficient. Most of the results have been found to be consistent with literature. Study reveals that static dielectric constant and band-gap are in accordance with the Penn model which validates our computed results. Moreover, static dielectric constant and static refractive index directly increases with pressure. Material preserves its positive value of refractive index at all pressures and therefore, it is not a negative index metamaterial. Plasma frequency increases directly with pressure that destabilize the under study material. Our results could be very useful for developing novel optoelectronic devices based on PZO suitable to work under extreme conditions. [ABSTRACT FROM AUTHOR]

The electronic structure of Ce1-xLaxPtIn is studied by means of ab initio full-potential local orbital basis (coherent potential approximation) (FPLO-CPA) and spin polarized relativistic Korringa-Kohn-Rostoker (SPRKKR- CPA) methods within the densities functional methodologies. In both methods, we have observed decrease of the density of states at the Fermi level versus of La concentration. The theoretical photoemission spectra of LaPtIn and CePtIn are compared with the experimental data and the agreement is good. We have also reported the optical properties of LaPtIn and CePtIn compounds obtained in GGA and GGA+U approximation. [ABSTRACT FROM AUTHOR]