Novel 122-type Ir-based superconductors BaIr2Mi2 (Mi = P and As): A density functional study

We explore the structural, electronic, bonding, mechanical, thermodynamic and superconducting properties of two newly discovered isostructural bulk superconductors barium iridium phosphide BaIr2P2 (Tc ∼ 2.1 K) and barium iridium arsenide BaIr2As2 (Tc ∼ 2.45 K). The optimized structural parameters of both the compounds show good agreement with the experimentally evaluated values. The replacement of P by As mostly affects the c value, whereas a remains approximately the same. Metallic conductivity is observed for both the superconductors. The analysis of DOS, Mulliken atomic populations and total charge density revel a complex bonding in BaIr2P2 and BaIr2As2 with ionic, covalent and metallic characteristics. Mechanical and dynamical stability of both the phases is confirmed by analyzing the elastic constant data. According to the calculated Pugh's ratio both the intermetallics are ductile in nature. Both the superconductors demonstrate anisotropic nature whereas the elastic anisotropy of BaIr2P2 is higher than that of BaIr2As2. The hardness of BaIr2P2 and BaIr2As2 is evaluated to be 6.92 GPa and 5.02 GPa respectively indicating the relative hardness of BaIr2P2 than that of BaIr2As2 superconductor. The Debye temperature of BaIr2P2 and BaIr2As2 has been calculated by using the elastic constant data to be 293.06 K and 258.47 K respectively. Finally the electronic specific heat coefficient, electron-phonon coupling constant, coulomb pseudo potential and superconducting critical temperature have been evaluated for both the compounds. We found weakly and moderately coupled bulk superconductivity in BaIr2P2 and BaIr2As2 with transition temperature 0.0057 K and 6 K respectively.