The Physical Properties of ThCr2Si2-type Nickel-based Superconductors BaNi2T2 (T = P, As): An ab-initio study

Employing the first-principles computations based on the density functional theory (DFT), we have investigated the structural, mechanical, electronic, bonding, optical and thermodynamics properties of newly discovered bulk superconductors BaNi2P2 (Tc ~3 K) and BaNi2As2 (Tc ~0.7 K). Our optimized lattice parameters are in good concurrence with the experimental records. The positive elastic constants reveal that both the superconductors are stable in nature. The analysis of the mechanical properties insures that both the phases are ductile in nature and show anisotropic behaviors. The analysis of the electronic band structures and density of states (TDOS and PDOS) reveals the metallic manners for both the compounds and the major contribution comes from Ni-3d states for both the phases. The calculations of the chemical bonding specify that a mixture of covalent, ionic and metallic bonds exist in both the superconductors. The high value of the dielectric constant of BaNi2As2 ensures that this compound may be used to manufacture high value capacitors. The large reflectivity in the low energy region indicates that both the compounds might be useful as coating materials to reduce solar heating. By using the elastic constants data the calculated Debye temperatures of BaNi2P2 and BaNi2As2 are 323.70 K and 272.94 K respectively, which are in good accordance with the experimental values. Finally we have calculated the thermal conductivity of these compounds which is 0.56 for BaNi2P2 and 0.46 for BaNi2As2.