The physical properties of ThCr2Si2- type nickel-based superconductors BaNi2T2 (T = P, As): An ab-initio study

Abstract

Employing first-principles computations depending on the density functional theory (DFT), we have investigated the structural, mechanical, electronic, bonding, optical and thermodynamics properties of the newly discovered bulk superconductors BaNi2P2 (Tc ∼ 3 K) and BaNi2As2 (Tc ∼ 0.7 K). Our optimized lattice parameters are in good agreement with the experimental results. 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 behavior. The analysis of the electronic band structures and density of states (TDOS and PDOS) reveals the metallic nature for both the compounds, and the major contribution comes from the 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 bothsuperconductors. The negative value of the real part of the dielectric constant of BaNi2T2 (T = P, As) also ensures that these compounds exhibit metallic behavior. The large reflectivity in the low energy region indicates that both the compounds might be useful as coating materialsfor reducing solar heating. By using the elastic constants information, the calculated Debye temperatures of BaNi2P2 and BaNi2As2 are 323.70 K and 272.94 K, respectively, which are in good accord 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.