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We report some unclarified physical properties of Ce3XY (X = Al, In and Y = C, N) inverse cubic perovskites by conducting a density functional theory (DFT) study. The elastic, mechanical, magnetic, thermodynamic and optical properties of these compounds were addressed. Obtained elastic data prove the mechanical stability, elastic anisotropy and brittle mechanical character for all investigated compounds. Vickers hardness values follow the Ce3InC > Ce3AlN > Ce3InN > Ce3AlC sequence. All compounds show ionic bonding except the Ce3AlC in which covalent bonding is dominant. Besides, all compounds exhibit ferromagnetic ordering. The calculated total magnetic moments arise between 2.22μB and 2.67μB. Their magnitudes follow Ce3InN > Ce3AlN > Ce3InC > Ce3AlC range. Temperature dependence of heat capacity, entropy, thermal conductivity and Debye temperature of the compounds exhibit identical characteristics of typical solids. Optical property results suggest that these compounds are both good optical absorbers and conductors, in particular for practical applications in the ultraviolet (UV) region. [ABSTRACT FROM AUTHOR]

We performed density functional theory (DFT) calculations to explore the electronic, optical, elastic and thermoelectric properties of Nb2WNi alloy for the first time by addressing the two different crystal structures (Cu2MnAl and Hg2CuTi) of the alloy. The calculated elastic constants results prove the mechanical stability for both crystal structures of the alloy. As well, Nb2WNi shows ductility for both crystal structures with a dominant metallic character. Nb2WNi alloy can be a good reflector, in particular for practical vacuum UV applications. It has also a high refractive index, especially in the IR region. The optical conductivity results support the use of Nb2WNi alloy for IR solar cell applications. The computed Seebeck coefficient values suggest the potential of Nb2WNi alloy as new thermoelectric material. [ABSTRACT FROM AUTHOR]

According to several previous works, Li2S2 occurs during discharge of lithium–sulfur (Li–S) batteries. Several information on the physical properties of this compound remain unknown including those of its ground state. In this work, a study of the pressure effect on the elastic and optoelectronic properties of Li2S2 in its tetragonal structure of P42/mnm space group was carried out. According to the previous works and according to the structural results, which have been obtained by GGA-PBE and optPBE-vdW funtionals, we have found that P42/mnm-Li2S2 energy is the lowest compared to other studied structures (P63/mmc, P-62m and Immm), this can indicate that P42/mnm space group structure may represent its ground state structure. The study of the pressure effect on the elastic properties has shown that P42/mnm-Li2S2 maintains its mechanical stability for a pressure range between 0 and 2.5 GPa. The study of the directional dependence of Young's modulus has shown that it is anisotropic and therefore indicates the elastic anisotropy of the studied compound. According to the electronic results, the fundamental band-gap of P42/mnm-Li2S2 is of an indirect nature, its values found by mBJ and GLLB-SC are close to each other. The pressure effect on the possible transitions between the valence band top and the conduction band bottom and on the variations of the refractive index and the absorption coefficient according to both optical directions has been studied by determining the dielectric function. The found optical results have shown that P42/mnm-Li2S2 has negative uniaxial birefringence. [ABSTRACT FROM AUTHOR]

We have studied the structural, elastic, electronic, phonon and thermodynamic properties of Ir3Ta and Rh3Ta alloys, usingab initiocalculations. For the L12phase, we report the calculated lattice constants, bulk modulus and elastic constants, and these values are compared with previously published values. We also derive the elastic constants from the values of the slopes of the acoustic branches in the phonon dispersion curves. The band structures show that both materials are metallic. The phonon dispersion curves, and their corresponding total and projected densities of states, are obtained using a linear response in the framework of the density functional perturbation theory. The specific heat capacity at constant volume and different temperatures is calculated, and this aspect is discussed using the quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]