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First-principle calculations using the Wien2k code and the GGA-mBJ exchange potential were used in the study of the thermodynamic, dynamic, chemical and elastic stability, as well as the electronic, optical and thermoelectric properties of Cs 2 (Sn, Pt, Te)I 6. The presence of an intermediate band in Cs 2 (Sn, Pt, Te)I 6 semiconductors confirmed by absorption peaks appeared at photon energy corresponding to the band gap enhances the efficiency of solar cells. The ideal band gap, high dielectric constants and optimal absorption make the double perovskites under study perform well in solar cells. The calculated minimum formation energy, Helmholtz free energy and phonon modes through the first Brillouin zone for the investigated Cs 2 (Sn, Pt, Te)I 6 family confirm their thermal, thermodynamic and dynamic stability. The acoustic phonon contribution modes come from the Cs-6s and I-5p electrons, while the Pt-6s, Sn-5p, Te-5p and I-5p electrons participate in the optical phonon modes. The narrowness of the upper valence band and the band gap in the visible region for C s 2 P t I 6 advantage this double perovskite in energy harvesting. The geometric Goldschmidt tolerance factor value between 0.8 and 1.0 and octahedral factor 0.41 indicate that C s 2 S n I 6 double perovskite is more stable. • We explore Cs 2 (Sn, Pt, Te)I 6 as potential thermoelectric materials because of their intrinsic p-type conductivity. • Efficient and high-performance thermoelectric materials such as Cs 2 (Sn, Pt, Te)I 6 exhibit low electronic thermal conductivity due to phonon-phonon scattering and optical emission. • The weaker elastic constants explain the large inter reticular distances and lower hardness and binding ionic forces. • The analysis of electronic structures proves that the band gap and optical gap in these materials are dictated by the energies of the empty (Sn-5s, Te-5p and Pt-6s) states at the lowest unoccupied band. • The efficiency of C s 2 S n I 6 , C s 2 T e I 6 and C s 2 P t I 6 in the conversion of heat into electrical energy is due to the p-type charge carriers, which give almost a factor of merite estimated at 83 %, 80.5 % and 78 %. • The considerable charge in the (Sn, Pt, Te)-I bonds due to a small difference in electronegativity and the hybridization between these levels reflects their covalent bonds. [ABSTRACT FROM AUTHOR]

We report ab initio density functional theory calculations of the structural, elastic, electronic and optical properties of the double perovskite oxides Sr 2 AlXO 6 (X=Ta, Nb, V). We have predicted a direct Г–Г band gap in Sr 2 AlXO 6 (X=Ta, Nb) and an indirect Г–X band gap for Sr 2 AlVO 6 . The fundamental band gap increases linearly when the pressure is enhanced in the range 0–20 GPa. The frequency dependent of complex dielectric function, absorption, reflectivity and electron energy loss function were investigated in the range 0–40 eV. Features such as lattice constant, bulk modulus, elastic constants, band structure, total and local densities of states have been computed. [ABSTRACT FROM AUTHOR]

Abstract: Some physical properties of the cubic perovskites CsXF3 (X = Ca, Sr and Hg) have been investigated using pseudopotential plane-wave method based on the density functional theory. The calculated lattice parameters within GGA and LDA agree reasonably with the available experimental data. The elastic constants and their pressure derivatives are predicted using the static finite strain technique. We derived the bulk and shear moduli, Young''s modulus, Poisson''s ratio and Lamé’s constants for ideal polycrystalline aggregates. The analysis of B/G ratio indicates that CsXF3 (X = Ca, Sr and Hg) are ductile materials. The thermal effect on the volume, bulk modulus, heat capacity and Debye temperature was predicted. [Copyright &y& Elsevier]

Abstract: Structural, elastic, electronic and magnetic properties of Mn3ZnC and Mn3GeC are investigated via ab initio calculations. Total energy calculations show that the ferromagnetic state is energetically more stable than the non-magnetic state at equilibrium volume. No found imaginary phonon frequency in the whole Brillouin zone for the two compounds supports their dynamical stability. The elastic parameters are predicted. The electrical conductivity is assured by the Mn-d electrons. The total moment comes principally from the transition metal Mn in both compounds. The magnetic moment of the Mn atom decrease considerably when the Zn atom is substituted by the Ge one. [Copyright &y& Elsevier]

Abstract: Various physical properties of the cubic perovskite-type oxide BiScO3 have been investigated using the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT). The computed equilibrium lattice parameters agree well with the available theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for BiScO3 polycrystalline aggregate. The analysis of the site-projected -decomposed density of states, charge transfer and charge density shows that bonding is predominantly of ionic nature. We distinguish hybridization between Sc-d states and - states in the valence bonding region. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermal effect on the lattice constant, bulk modulus, heat capacities and thermal expansion coefficient is calculated. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic, optical and thermal properties of the semiconductor perovskite CsPbCl3 were investigated using the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA) and local density approximation (LDA). The computed lattice constant agrees reasonably with experimental and theoretical ones. The CsPbCl3 crystal behaves as ductile material. The valence bands are separated from the conduction bands by a direct band gap R–R. We distinguished hybridization between Pb-p states and Cl-p states in the valence bonding region. Under compression at P=30GPa, this material will have a metallic character. The thermal effect on the lattice constant, bulk modulus, Debye temperature and heat capacity C V was predicted using the quasi-harmonic Debye model. To the author''s knowledge, most of the studied properties are reported for the first time. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic, optical and thermodynamic properties of the perovskite chloride CsCdCl3 were investigated using the pseudo-potential plane wave (PP-PW) within the Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA). The computed lattice parameter agrees well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal rigidity and mechanical stability have been discussed. Energy band structure shows that the investigated material is indirect energy band gap semiconductor. The static dielectric constant and static refractive index are indeed, proportional to the fundamental indirect band gap. The thermal effect on the lattice parameter, bulk modulus, volume expansion coefficient, Grüneisen parameter, heat capacities and Debye temperature were predicted using the quasi-harmonic Debye model. To the best of the authors’ knowledge, most of the studied properties are reported for the first time. [Copyright &y& Elsevier]

Abstract: The stability, structural parameters, elastic constants, electronic and optical properties of perovskites CsCaH3 and RbCaH3 were investigated by the density functional theory. The calculated lattice parameters are in agreement with previous calculation and experimental data. The energy band structures, density of states, born-effective-charge and Mulliken charge population were obtained. The perovskites CsCaH3 and RbCaH3 present a direct band gap of 3.15eV and 3.27eV at equilibrium. The top of the valence bands reflects the s electronic character for both structures. Furthermore, the absorption spectrum, refractive index, extinction coefficient, reflectivity, energy-loss spectrum, and dielectric function were calculated. The origin of the spectral peaks was interpreted based on the electronic structures. The static dielectric constant and refractive index are indeed, inverse proportional to the direct band gap. [Copyright &y& Elsevier]

Abstract: We present structural, elastic, electronic and optical properties of the perovskites SrMO3 (M=Ti, and Sn) for different pressure. The computational method is based on the pseudo-potential plane wave method (PP-PW). The exchange-correlation energy is described in the generalized gradient approximation (GGA). The calculated equilibrium lattice parameters are in reasonable agreement with the available experimental data. This work shows that the perovskites SrTiO3, and SrSnO3 are mechanically stable and present an indirect band gaps at the Fermi level. Applied pressure does not change the shape of the total valence electronic charge density and most of the electronic charge density is shifted toward O atom. Furthermore, in order to understand the optical properties of SrMO3, the dielectric function, absorption coefficient, optical reflectivity, refractive index, extinction coefficient and electron energy-loss are calculated for radiation up to 80 eV. The enhancement of pressure decreases the dielectric function and refractive indices of SrTiO3 and SrSnO3. [Copyright &y& Elsevier]