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The electronic structure, elastic moduli, as well as thermodynamic features of the ferromagnetic Cd0.75TM0.25S (TM = Os or Ir) compounds in the zinc-blende phase were investigated by employing the "generalized gradient approximations" parametrized by Wu and Cohen combined with the "modified Becke-Johnson (TB-mBJ)" as well as the hybrid functional (HSE06). The predicted total magnetic moments for the transition metals Os and Ir are 4.0 μB and 3.0 μB with TB-mBJ and are 2.0 μB and 3.0 μB using the hybrid functional (HSE06) for compounds Cd0.75Os0.25S and Cd0.75Ir0.25S, respectively. The generation of magnetic moments and spin-polarization in these alloys is directly linked to the contribution coming from TM-5d states. The ferromagnetic properties of these alloys were predicted by the computed exchange constants Besides, the increase in the porosity paramete N 0 α and N 0 β . The Total and partial densities of states (TDOS/PDOS) and the behavior of electronic band structures (EBS) were also calculated to describe the ferromagnetic semiconducting and half-metallic (HM) characteristics with TB-mBJ and the hybrid functional (HSE06). According to the findings, Cd0.75Os0.25S is a half-metallic ferromagnetic (HM) material with a full polarization spin distribution of electrons at the Fermi energy level, exhibiting metallicity for the majority spin and a semiconducting nature for the minority spin. In contrast, Cd0.75Ir0.25S is a ferromagnetic half-semiconductor (HSC) with two distinct gaps depending on the up and down spin configurations. Calculations of the elastic constants, Young and shear moduli reveal that the compound Cd0.75TM0.25S (TM = Os or Ir) is mechanically stable, has a high degree of anisotropy, and is naturally ductile. Furthermore, the "quasi-harmonic Debye model" was performed to examine the thermodynamic properties of the studied compounds, including the thermal capacity, entropy and Debye temperature. [ABSTRACT FROM AUTHOR]

In this work, the band structure feature, charge carrier mobility, optical properties, and photocatalytic performance of platinum-based vacancy-ordered double perovskites Rb2PtX6 (X = Cl, Br, and I) are investigated. The results show the semiconducting character of all three materials with band gap values equal to 3.39 eV, 2.76 eV, and 1.45 eV, for Rb2PtCl6, Rb2PtBr6, and Rb2PtI6, respectively. Furthermore, the calculated electron and hole effective masses yield a higher relative mass of hole-electron pairs (D), resulting in a slow recombination rate in these materials. The optical properties are also calculated, where the entitled materials show high absorption intensities in the visible and ultraviolet regions. Moreover, it is discovered that the Rb2PtCl6 and Rb2PtBr6 compounds can produce both oxygen and hydrogen at the same time. In contrast, the Rb2PtI6 material has a poor water-splitting ability and may be a promising photocatalyst for CO2 photoreduction. [ABSTRACT FROM AUTHOR]

The optimized structural parameters, electronic structure, and thermoelectric coefficients of the chalcopyrite alloys Cu1–xNaxTlSe2, with x = 0.00, 0.25, and 0.50 were studied through density functional theory calculations. The Wu–Cohen generalized gradient and the Tran–Blaha modified Becke–Johnson approximations have been employed to describe the exchange–correlation potential. Energy band structure analysis reveals that CuTlSe2 is a semi-metal, while Cu0.25Na0.75TlSe2 and Cu0.50Na0.50TlSe2 alloys are semiconductors with gaps of approximately 0.17 eV and 0.35 eV, respectively. The total and partial densities of states were calculated and discussed. Examining the charge density, we point out the formation of the Na–Se ionic bond when Cu is replaced by the Na atom, which is responsible for the metal–semiconductor transition in the Cu1–xNaxTlSe2 alloys. Moreover, variations of the Seebeck coefficient, electrical conductivity, electronic and lattice thermal conductivity, power factor, and figure of merit of the Cu1–xNaxTlSe2 alloys with temperature and chemical potential were explored. The obtained results show that the value of the figure of merit increases when doping CuTlSe2 with sodium to reach 0.46 and 0.87 for p-type Cu0.75Na0.25TlSe2 and n-type Cu0.50Na0.50TlSe2, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates in detail the structural, magnetic, and optoelectronic properties of Cd0.75TM0.25S (TM = Os and Ir) alloys having a zinc-blende structure of the ferromagnetic phase using the full potential linearized augmented plane-wave (FP-LAPW) method as implemented in the Wien2k package. The exchange–correlation potential was treated with the generalized gradient approximation (GGA). Moreover, the GGA + U + SO approximation (where U denotes the Hubbard Coulomb energy and SO is the spin orbit coopling) are employed to treat the d electrons properly. The analysis of the values of formation energy, formation enthalpy, phonon spectra and the exchange interaction parameters show that the investigated alloys are stable and can be synthesized. The densities of states (DOS) indicate that Cd0.75TM0.25S (TM = Os and Ir) exhibits metallic nature using both GGA and GGA + SO. The half-metallic nature for Cd0.75Os0.25S and the ferromagnetic half-semiconductor nature for Cd0.75Ir0.25S have been predicted by GGA + U. Both considered alloys become ferromagnetic-semiconductors by using GGA + SO + U, where the computed band gaps are 0.52 for Cd0.75Os0.25S and 0.72 for Cd0.75Ir0.25S. The dielectric function's real and imaginary portions ε ′ ω , ε ″ ω , absorption coefficient α (ω) , and refractive index n (ω) were evaluated using a radiation range up to 30 eV. For CdS, the observed results are on par with previously published experimental and theoretical results. Our findings imply that these materials might be of potential use in future spintronic devices. [ABSTRACT FROM AUTHOR]

In this study, an analysis of the effect of Na substitution on the electronic, structural and thermoelectric (TE) properties of the Li2CuAs material is presented. The study is performed by employing the full-potential linearized augmented plane wave plus local orbital method designed within the density functional theory. To carry out the calculations related to the band structure, generalized gradient approximation by Wu-Cohen (WC-GGA) in combination with Trans Blaha-modified Becke-Johanson mBJ (TB-mBJ) potential is employed. Our results at the level of the WC-GGA approach show that there is no bandgap, whereas, at the level of the TB-mBJ approximation, the material displays bandgap with Na substitution, which is found to be further increased with the increasing Na concentration. To understand the role of different electronic states on the bandgap structure, the total and partial densities of states are also analysed. Furthermore, the temperature effect on the Seebeck coefficient, electronic thermal conductivity, electrical conductivity, power factor and figure of merit are computed. Our obtained results of the TE properties of Li2CuAs at different Na compositions suggest that this compound is a potential candidate for thermoelectricity. [ABSTRACT FROM AUTHOR]

Based on the full-potential linearized augmented plane wave (FP-LAPW) method, we have investigated the electronic, structural, magnetic and optical properties of Cd0.9375TM0.0625S (TM = Mn, Fe, Co and Ni) compounds in the zinc-blende (ZB) ferromagnetic phase. The magnetic and electronic properties are treated using the PBE-GGA and TB-mBJ approximations. CdS is well known as a non-magnetic semiconductor. When CdS is doped with a transition metal (TM), Cd0.9375TM0.0625S (TM = Mn, Fe, Co) changes to half-semiconductors (HSC) and Cd0.9375Ni0.0625S to a half-metal (HM). It is found that the 3d-t2g states of the transition metal are responsible for generating spin polarization and magnetic moment in these compounds. All the considered compounds are ferromagnetic and the calculated total magnetic moment increases from 2 to 5 µB moving from Ni to Mn. The optical properties exhibited new peaks in the visible and ultraviolet regions due to the effect of free-carrier absorption related to the magnetic impurities. Our results show very good agreement to previous theoretical and experimental data. The results presented herein imply that TM-doped CdS has potential for applications in spintronic and optoelectronic device sectors in a wide energy range of the light spectrum from visible to ultraviolet. [ABSTRACT FROM AUTHOR]

The first-principle calculations of density functional theory were used to study the structural, electronic, magnetic, mechanic, and half-metallic behavior of Y2MnZ (Z = Al, Ga, In) within the spin generalized gradient approximation. These compounds can be experimentally synthesized due to their negative values of the calculated formation energies. Our calculations indicate that they are more stable in Cu2MnAl-type structure. The Hg2CuTi-type structure displays half-metallic characteristic with 100% spin polarization at the Fermi level. The value of calculated magnetic moment has an integer value of 2μB for Y2MnZ (Z = Al, Ga, In) in the Hg2CuTi-type structure which well matches with magnetic moments predicted from Slater–Pauling rule. Therefore, the Y2MnZ (Z = Al, Ga, In) in the Hg2CuTi-type structure is predicted to be a candidate for possible spintronics applications. [ABSTRACT FROM AUTHOR]

The thermoelectric (TE) materials convert heat directly into electricity or transport thermal energy by the application of an electric current. This class of materials has been known for over a century, but the limited efficiency has slowed down their development. However, due to the discovery of new materials and the control of dimensionality, thermoelectric has regained its interest in recent years. Inspired by the fascinating properties of 2D graphite many new 2D materials are designed. The prediction of low dimensional materials and the exploration of their electronic and thermoelectric properties have demonstrated that the low dimensional approach is effective for the enhancement of the figure of merit ZT. In this review, we discuss the thermoelectricity phenomena and the latest theoretical investigations performed in developing and designing new 2D thermoelectric materials. Besides, the different strategies to improve the thermoelectric performance that could be used in the new 2D thermoelectric materials will be highlighted. [ABSTRACT FROM AUTHOR]

A number of ternary-semiconductor oxides have shown promise for potential applications in catalysis, thermoelectricity, optoelectronics and electrochemistry. In this work, the thermoelectric and optoelectronic properties of La 2 Pd 2 O 5 compound are studied by the full-potential linearized augmented plane wave method based on density functional theory. The electronic band structure shows an indirect band gap of 1.342 eV for La 2 Pd 2 O 5 . Partial and total density of states indicate strong hybridization among different electronic orbitals. The upper part of the valence band is dominated by the Pd-d and O-p states, while the lower conduction band originates mainly from the Pd-d state. Dielectric functions including the imaginary and real parts, along with other optical constants, such as absorption coefficient, energy loss function, reflectivity and refractive index, have been reported for the first time. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient and power factor with variation in temperature are also presented and discussed using semi-classical Boltzmann transport theory for the first time for La 2 Pd 2 O 5 . It has been found that La 2 Pd 2 O 5 has attractive optoelectronic and thermal properties that can make it a suitable candidate for efficient thermoelectric and optoelectronic device applications. [ABSTRACT FROM AUTHOR]

We report, in this work, a theoretical study of electronic and transport (thermoelectric) properties of some superconductor nickel-based antiperovskite XNNi3 (X = Mg, Al, Cu, Zn, Ga, Ag, Cd, In, Sn, Sb, Pt and Pb) using first-principles calculations with the full-potential linearized augmented plane wave (FPLAPW) method based on the density functional theory (DFT) as implemented in the WIEN2k package. Electronic properties are calculated and show that the studied materials are of metallic type which is in good agreement with experimental data. The Seebeck coefficient, thermal conductivity, electrical conductivity and figure of merit were reported. The results obtained show that the zinc (Zn) and silver (Ag) materials are characterized by a high value of the figure of merit at room temperature (300 K) which is respectively 0.86 and 1.02 in a p-type region. In the case of the transition metals, the maximum values of S increase in going from the Pt atom to the Zn atom and then decrease for the Cd atom. Furthermore, the Wiedemann-Franz law which states that the ratio of thermal to electrical conductivity for metals is constant is well verified in this work. The electric conductivity values are almost invariant with the temperature except for the case of MgNNi3 and AgNNi3 compounds in which it increases with T slightly. So, the superconducting materials based on silver and zinc are the best for the thermoelectric applications at room temperature due to the very important value of the factor of merit and the Seebeck coefficient obtained. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, in this work we report the structural, electronic and, for the first time, thermoelectric properties of CuNMn3 cubic antiperovskite. The structural properties are explored using GGA and GGA+U approximations. Structural optimization shows that the compound is stable in the ferrimagnetic phase, and the electronic properties confirm the metallicity of this compound. At room temperature, high values of the Seebeck coefficient are obtained between - 0.8 and 0.5 μ(eV) chemical potential, whereas outside this region the Seebeck coefficient diminishes. Also, thermal conductivities are minimal in this region of chemical potential; therefore, the material can be used to achieve thermocouples. Thermal conductivity is high for 900 K. The maximum electrical conductivity is obtained at 0.38 μ(eV) chemical potential, with a value of 4.15×1020(Ωms)-1. The figure of merit ZT values obtained are still low, so for thermoelectric applications of the material, it is necessary to improve the figure of merit coefficient by doping the material with a suitable element. [ABSTRACT FROM AUTHOR]

We report the results of the full-potential linearized augmented plane wave (FP-LAPW) calculations on the structural, elastic, optoelectronic and magnetic properties of $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ spinel. Both the generalized gradient approximation (GGA) and Trans-Blaha modified Becke-Johnson potential (TB-mBJ) are used to model the exchange-correlation effects. The computed lattice parameter, internal coordinate and bulk modulus are in good agreement with the existing experimental data. According to the calculated elastic moduli, $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ is mechanically stable with a ductile nature and a noticeable elastic anisotropy. The ferromagnetic phase of $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ is energetically favourable compared to non-magnetic one, with a high magnetic moment of about 8.15 $$\upmu _{\mathrm{B}}$$ . The calculated band structure demonstrates that the title compound is a direct band gap semiconductor. The TB-mBJ yields a band gap of $$\sim $$ 1.86 and $$\sim $$ 2.17 eV for the minority and majority spins, respectively. The calculated optical spectra reveal a strong response in the energy range between the visible light and the extreme UV regions. [ABSTRACT FROM AUTHOR]

The elastic, electronic and thermodynamic properties of fluoro-perovskite KZnF have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Also, we have used the Engel and Vosko GGA formalism (GGA-EV) to improve the electronic band structure calculations. The calculated structural properties are in good agreement with available experimental and theoretical data. The elastic constants C are calculated using the total energy variation with strain technique. The shear modulus, Young's modulus, Poisson's ratio and the Lamé coefficients for polycrystalline KZnF aggregates are estimated in the framework of the Voigt-Reuss-Hill approximations. The ductility behavior of this compound is interpreted via the calculated elastic constants C. Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron charge density. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk modulus, lattice constant, heat capacities and the Debye temperature with pressure and temperature are successfully obtained. [ABSTRACT FROM AUTHOR]