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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]

This study employed density functional theory (DFT) embedded in Wien2K code to evaluate the physical features of the XGeCl3 (X = Rb/Cs) cubic halide perovskites. The structural optimization has been performed considering generalized gradient approximation (GGA) and electronic properties have been computed considering modified Becke‐Johnson potential (mBJ). The formation energy and phonon dispersion analysis establish the stability of the investigated compounds. Mechanical stability is further confirmed by the computed diverse elastic coefficients. It has been discovered that the examined substances are naturally ductile. The refractive index, reflectivity, and absorption coefficient, are among the optical parameters that have been estimated and analyzed. Interesting results have been obtained for the transport properties of XGeCl3 (X = Rb/Cs). The XGeCl3 (X = Rb/Cs) exhibits a high Seebeck coefficient (X = Rb/Cs) and the largest figure of merit (about 0.99), indicating significant potential for thermoelectric applications. [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]

To study the structural, electronic, and optical properties of the half-Heusler CoCrZ (Z = Al, Ga), we have performed ab initio calculations using the full-potential with the mixed basis (APW + lo) method within the generalized gradient approximation. The structural properties as well as the band structures, and total and atomic projected densities of states are computed. From electronic band structures we have found that both compounds have a semimetallic nature. We also studied the evolution of electronic structure of CoCrAl under external hydrostatic pressure. It is found that the pseudo gap around the Fermi level increases continuously with increasing pressure, while the electronic density of states at the Fermi level does not change significantly. Furthermore, the optical properties, such as the dielectric function and refractive index were evaluated and discussed under pressure up to 20 GPa, and the electrical conductivity and electron energy loss were calculated for radiation up to 30 eV. The same way, we have studied the magnetic properties of CoCrAl for lattice expansion up to a = 1.1[a.sub.0] where a transition from the paramagnetic phase to the half-metallic phase is expected. PACS Nos.: 71.15.Mb, 71.15.Ap, 71.20.Be. Nous completons un calcul ab initio utilisant la methode du potentiel total avec base mixte (APW+lo) a l'interieur de l'approximation du gradient generalise, les proprietes structurales, electroniques et optiques des alliages demi- Heusler CoCrZ (Z = Al et Ga). Nous calculons les proprietes structurales, les structures de bande, les densites d'etats totales et a projection atomique. A partir des structures de bandes, nous trouvons que les deux composes ont une nature semi-metallique. Nous etudions aussi revolution de la structure electronique de CoCrAl sous pression hydrostatique externe. Nous trouvons que le pseudo-gap autour du niveau de Fermi croit continuellement avec la pression, alors que la densite d'etats electroniques au niveau de Fermi ne change pas de facon significative. Nous evaluons et analysons aussi les proprietes optiques, comme la fonction dielectrique et l'indexe de refraction, a des pression allant jusqu'a 20 GPa, et nous calculons la conductivite electrique et la perte d'energie electronique sous des radiations jusqu'a 30 eV. De facon similaire nous etudions les proprietes magnetiques de CoCrAl pour une expansion de reseau allant jusqu'a a = 1.1[a.sub.0], ou nous attendons une transition d'une phase paramagnetique a une phase demi metallique. [Traduit par la Redaction], 1. Introduction During the last two decades first principle methods have become the most powerful probes for calculating various physical properties of solids such as the structural, electronic, mechanical and [...]

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]