Search

The electronic structure and optical properties of Rb2Cu2Sb2S5, Cs2Cu2Sb2S5, and Rb8Cu6As8S19 were investigated from first principles based on Engel-Vosko generalized gradient approximation (EV-GGA). The calculated band structures and density of states confirm that these compounds have an indirect bandgap. The bands near the Fermi level were mainly contributed from Cu-3 d states along with a small participation of S-3 p states. The partial density of states shows that Cs and Rb elements are bonded ionically to sulfur, whereas Cu, Sb, As, and S element show covalent bonds with each other. From the electronic structure and using EV-GGA, the frequency-dependent optical parameters such as the real and imaginary parts of the dielectric functions, energy loss function, and reflectivity were calculated. These optical parameters prove that these compounds are potentially interesting for the field of optoelectronic and optical devices. The temperature-dependent thermoelectric properties such as the electrical conductivity, Seebeck coefficient, thermal conductivity, and power factor were calculated based on combination of DFT output and Boltzmann transport theory. [ABSTRACT FROM AUTHOR]

Sr3GaN3 and Sr6GaN5 could be promising potential materials for applications in the microelectronics, optoelectronics and coating materials areas of research. We studied in detail their structural, elastic, electronic, optical as well as the vibrational properties, by means of density functional theory framework. Both of these ternaries are semiconductors, where Sr3GaN3 exhibits a small indirect gap whereas Sr6GaN5 has a large direct gap. Indeed, their optical properties are reported for radiation up to 40 eV. Charge densities contours, Hirshfeld and Mulliken populations, are reported to investigate the role of each element in the bonding. From the mechanical properties calculation, it is found that Sr6GaN5 is harder than Sr3GaN3, and the latter is more anisotropic than the former. The phonon dispersion relation, density of phonon states and the vibrational stability are reported from the density functional perturbation theory calculations. [ABSTRACT FROM AUTHOR]

The present paper reports the analysis of surface decoration on the structural, electronic, and optical properties of (n,0) ZnO nanotubes, performed by means of a density function theory based ab-initio approach. Fe functionalization induced buckling in ZnO nanotubes affects its electronic and optical properties. Increase in Fe functionalization leads to better stability of ZnO nanotube and shows enhanced metallic character. The possibility of its use in optoelectronics has been analyzed in terms of dielectric constant, absorption coefficient, and refractive index. In another observation, the high sensitivity of the HCN molecule for the Fe-incorporated ZnO nanotube suggests it as a potential gas sensor.HCN-adsorbed Fe-ZnO nanotube, electron difference density, and PDOS analysis of different orbitals. [ABSTRACT FROM AUTHOR]

We combined a density functional theory (DFT) and Boltzmann transport theory to investigate the optoelectronic and thermoelectric properties of the monoclinic selenide Cu 5 Sn 2 Se 7 compound. The present selenide is found metallic and has shown similarities with the recent selenides based on transition metals. The Fermi level is surrounded by the Cu -d , Sn -s and Se -p states along with the small contribution of Cu- s/p , Sn- p/d and Se -d states. The investigated optical properties illustrated that the major transitions take place from Cu -d and Se -p states below E F to the Sn -s states above E F . DFT calculations were combined to Boltzmann transport theory to extract the thermoelectric properties depending on temperature such as the resistivity, thermal and electrical conductivity, Seebeck coefficient and figure of merit (ZT). Our theoretical thermoelectric properties show a very close agreement with available experimental data. [ABSTRACT FROM AUTHOR]

Li 2 CdGeS 4 and Li 2 CdSnS 4 compounds are diamond-like semiconductors (DLSs) and have been investigated to explore their electronic structure and optical properties for potential optoelectronic applications. Density functional theory within the modified Becke–Johnson (mBJ) exchange potential shows that the band structures exhibit direct band gap semiconductors at Γ with optical band gaps of 2.461 and 3.16 eV for Li 2 CdGeS 4 and Li 2 CdSnS 4 respectively. Along side showing that both compounds are optically active materials, our finding exhibit a nice harmony with experimental measured band gaps (3.10 eV and 3.26 eV for Li 2 CdGeS 4 and Li 2 CdSnS 4 ). Charge densities iso-surfaces and two-dimensional maps were reported to determine the effect of Sn/Ge on the bonding characteristics of both DLSs. The static dielectric constant ε 1 ( 0 ) and static refractive index n ( 0 ) are decreasing when Ge is replaced by Sn. Consequently, the possibility to tune the band gap for both DLSs could lead us to target particular optoelectronic applications in the next future such LED and solar cells. [ABSTRACT FROM AUTHOR]

Chalcopyrite semiconductors have attracted much attention due to their potential implications in photovoltaic and thermoelectric applications. First principle calculations were performed to investigate the electronic, optical and thermoelectric properties of the Zintl tetragonal phase ACdGeAs 2 (A = K, Rb) using the full potential linear augmented plane wave method and the Engle–Vosko GGA (EV–GGA) approximation. The present compounds are found semiconductors with direct band gap and covalent bonding character. The optical transitions are investigated via the dielectric function (real and imaginary parts) along with other related optical constants including refractive index, reflectivity and energy-loss spectrum. Combining results from DFT and Boltzmann transport theory, we reported the thermoelectric properties such as the Seebeck’s coefficient, electrical and thermal conductivity, figure of merit and power factor as function of temperatures. The present chalcopyrite Zintl quaternary arsenides deserve to be explored for their potential applications as thermoelectric materials and for photovoltaic devices. [ABSTRACT FROM AUTHOR]

Due to growing demand on discovering new materials for light-emitting diodes devices, many efforts were made to discover and characterize new inorganic materials such as phosphors. Using the full potential method within density functional theory the electronic and optical properties of BaAl 2 Si 3 O 4 N 4 and BaAlSi 4 O 3 N 5 semiconductors have been investigated. The electronic structure and the optical properties of these phosphors were calculated through a reliable approach of modified Beck-Johnson (mBJ) approach. We found that BaAl 2 Si 3 O 4 N 4 and BaAlSi 4 O 3 N 5 have wide direct band gaps positioned at Γ about 5.846 and 4.96 eV respectively. The optical properties, namely the dielectric function, optical reflectivity, refractive index and electron energy loss, are reported for radiation up to 15 eV. Our study suggests that BaAl 2 Si 3 O 4 N 4 and BaAlSi 4 O 3 N 5 could be promising materials for applications in the LEDs devices and optoelectronics areas of research. [ABSTRACT FROM AUTHOR]

Electronic structure and optical properties of SnGa 4 Q 7 (Q = S, Se) compounds were investigated using a full potential linearized augmented plane wave method based on density functional formalism. Electronic band structures show an indirect semiconducting wide band gap two different approaches (EV-GGA and mBJ). The band gap values are estimated at 2.90 (2.25 eV) and 3.11 (2.49 eV) for EV-GGA and mBJ for SnGa 4 S 7 (SnGa 4 Se 7 ), respectively. Densities of states show that Sn-5 s and S/Se-3 p /4 p states are dominating the region around Fermi level form valence band maximum and conduction band minimum. The computed electronic charge density contours demonstrate that SnGa 4 Q 7 (Q = S, Se) show a mixture between ionic and covalent characters. Optical parameters including the dielectric constant, absorption coefficient, reflectivity, refractive index, energy loss function, and birefringence are also reported to investigate the potential role of SnGa 4 Q 7 (Q = S, Se) compounds for solar energy conversion application. [ABSTRACT FROM AUTHOR]

Abstract: By employing the state of art first principles approaches, comprehensive investigations of a very promising hydrogen storage material, Mg2FeH6 hydride, is presented. To expose its hydrogen storage capabilities, detailed structural, elastic, electronic, optical and dielectric aspects have been deeply analysed. The electronic band structure calculations demonstrate that Mg2FeH6 is semiconducting material. The obtained results of the optical bandgap (4.19eV) also indicate that it is a transparent material for ultraviolet light, thus demonstrating its potential for optoelectronics application. The calculated elastic properties reveal that Mg2FeH6 is highly stiff and stable hydride. Finally, the calculated hydrogen (H2) storage capacity (5.47 wt.%) within a reasonable formation energy of −78kJmol−1, at room temperature, can be easily achievable, thus making Mg2FeH6 as potential material for practical H2 storage applications. [Copyright &y& Elsevier]

Highlights: [•] Mutual alloying of XAs (X=Ga, In, Al) materials is investigated with DFT. [•] XAs materials are suitable for optoelectronic and solar energy applications. [•] Energy gap of Ga1−xAl x As and In1−xAl x As was found to be increased with x. [•] Mutual alloying with different concentrations is useful to tune their properties. [Copyright &y& Elsevier]

Abstract: The current study investigates the structural, elastic, electronic and optical properties of CeO2, PrO2 and TbO2 using the full potential (linearized) augmented plane wave plus local orbital method within the Wu–Cohen generalized gradient approximation (GGA) with Hubbard (U) correction and spin–orbit coupling (SOC). The GGA+U implementation lead us to describe correctly the relativistic effect on 4f electrons for CeO2. We clarify that the inclusion of the Hubbard U parameter and the spin–orbit coupling are responsible for the ferromagnetic insulating of PrO2 and TbO2. The magnetic description is achieved by the spin-density contours and magnetic moment calculations, where we show the polarization of oxygen atoms from the rare earth atoms. The mechanical stability is shown via the elastic constants calculations. The optical properties, namely the dielectric function and the reflectivity are calculated for radiation up to 12eV, giving interesting optoelectronic properties to these dioxides. [Copyright &y& Elsevier]

We have carried an analytical review of electronic and optical properties of bulk and slab CaTiO 3 :Eu+2 by employing the first-principle calculations that are linked with Density Functional Theory (DFT). The properties of bulk and slab have been explored using the generalized gradient approximation with the Hubbard parameter (GGA ​+ ​U) approach. Electronic properties, such as band structure, total and partial density of states (TDOS and PDOS) have been calculated for bulk and slab CaTiO 3 :Eu+2. Based on the obtained results, the direct band gaps are examined for both bulk and slab with bandgap values 2.839eV and 0.289eV respectively. Besides, the transitions are also observed which are mainly due to O-p, Eu-f, Ti-d, and Eu-d for both bulk and slab. The role of band structure calculation, regarding optical properties, is discussed. Plasmon-energy is the main reason for peaks of the energy loss function,12.5 ​eV, for both bulk and slab. The static values of dielectric functions, absorption coefficient, and refraction are also calculated. Our results revealed that slab CaTiO3:Eu+2 material is more suitable for optical devices due to its direct bandgap nature and small bandgap value (0.289eV). Image 1 • An analytical review of electronic and optical properties of bulk and slab CaTiO 3 :Eu+2 has been carried out. • The properties of bulk and slab have been explored using the GGA with the Hubbard parameter (GGA ​+ ​U) approach. • Electronic properties, have been calculated for bulk and slab CaTiO 3 :Eu+2. • The transitions are observed which are mainly due to O-p, Eu-f, Ti-d, and Eu-d for both bulk and slab. • The role of band structure calculation, regarding optical properties, is discussed. [ABSTRACT FROM AUTHOR]