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Using first‐principles calculations, the structural, elastic, and electronic properties of MoAlB have been investigated. The optimized lattice constants exhibit fair agreement with the experimental results. The computed elastic constants satisfy the mechanical stability conditions for MoAlB. The Mo‐based boride MoAlB is elastically anisotropic and classified as brittle material. This boride is expected to be thermally conductive due to its high Debye temperature of 693 K. The metallic conductivity of this compound is predicted by means of electronic structure calculations. The chemical bonding in MoAlB is basically covalent that is assured with the results of DOS, Mulliken population, and charge density distribution. The hardness value of 11.6 GPa for MoAlB suggests that it is relatively soft compared to many others borides. The Fermi surface is formed due to low dispersive Mo 4d‐like bands, which makes the compound a conductive one.

Perovskite-type structures (ABO3) have received significant attention because of their crystallographic aspects and physical properties, but there has been no clear evidence of a superconductor with a double-perovskite-type structure, whose different elements occupy A and/or B sites in ordered ways. In this report, hydrothermal synthesis at 220 °C produced a new superconductor with an A-site-ordered double perovskite structure, (Na(0.25)K(0.45))(Ba(1.00))3(Bi(1.00))4O12, with a maximum T(c) of about 27 K.

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Perovskite‐type structures (ABO3) have received significant attention because of their crystallographic aspects and physical properties, but there has been no clear evidence of a superconductor with a double‐perovskite‐type structure, whose different elements occupy A and/or B sites in ordered ways. In this report, hydrothermal synthesis at 220 °C produced a new superconductor with an A‐site‐ordered double perovskite structure, (Na0.25K0.45)(Ba1.00)3(Bi1.00)4O12, with a maximum Tc  of about 27 K.

The effects of M atomic species mixing on the structural, elastic, electronic, thermodynamic and charge transport properties of newly synthesized MAX phase (Zr 1-x Ti x ) 2 AlC (0 ≤ x ≤ 1) solid solutions have been studied for the first time by means of density functional theory (DFT) based first principles calculations. The lattice constants in good accord with the experimental results, are found to decrease with Ti content. The elastic constants, C ij , and the other polycrystalline elastic moduli have been calculated. The elastic constants satisfy the mechanical stability conditions of these solid solutions. The constants C 11 , C 33 and C 44 are found to increase with Ti contents up to x = 0.67, thereafter these decrease slightly. A reverse trend is followed by C 12 and C 13 . The elastic moduli are also found to increase up to x = 0.67, beyond which these moduli go down slightly. Pugh"s ratio and Poisson"s ratio both confirm the brittleness of (Zr 1-x Ti x ) 2 AlC. Different anisotropy factors revealed the anisotropic character of these solid solutions. A non-vanishing value of the electronic energy density of states (EDOS) at the Fermi level suggests that (Zr 1-x Ti x ) 2 AlC are metallic in nature. A mixture of covalent, ionic and metallic bonding has been indicated from the electronic structure with dominant covalent bonding due to hybridization of Zr-4d states and C-2p states. The variation of elastic stiffness and elastic parameters with x is seen to be correlated with partial DOS (PDOS) and charge density distribution. The calculated Debye temperature and minimum thermal conductivity are found to increase with Ti contents, while melting temperature is the highest for x = 0.67. The solid solution with x = 0.67 shows improved mechanical and thermal properties compared to that of the two end members Zr 2 AlC and Ti 2 AlC. The study of charge transport properties of (Zr 1-x Ti x ) 2 AlC reveals the metallic nature with saturated resistivity. The maximum power factor (S 2 /=11.1×10 10 Wm -1 K -2 s -1 ) is obtained at 400 K for (Zr 1-x Ti x ) 2 AlC.

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