Ab-initio insights into the physical properties of XIr3 (X = La, Th) superconductors: A comparative analysis

Abstract

Here we report the structural, elastic, bonding, thermo-mechanical, optoelectronic and superconducting state properties of recently discovered XIr₃ (X = La, Th) superconductors utilizing the density functional theory (DFT) using two different exchange-correlations functionals. The elastic, bonding, thermal and optical properties of these compounds are investigated for the first time. The calculated lattice and superconducting state parameters are in reasonable agreement to those found in the literature. In the ground state, both the compounds are mechanically stable and possess highly ductile character, high machinability, low Debye temperature, low bond hardness and significantly high melting point. The thermal conductivities of the compounds are found to be very low which suggests that they can be used for thermal insulation purpose. The population analysis and charge density distribution map confirm the presence of both ionic and covalent bonds in the compounds with ionic bond playing dominant roles. The calculated band structure and DOS profiles indicate metallic character of XIr₃ compounds. It is also found from the DOS profile that the Ir 5d-states dominate near the Fermi level. Unlike the significant anisotropy observed in elastic and thermal properties, all the optical constants of XIr₃ compounds exhibit almost isotropic behavior. The optical parameters’ profiles correspond very well with the electronic band structure and DOS features. We have estimated the superconducting transition temperature (T_c) of XIr₃ compounds in this work. The calculated values of T_c for LaIr₃ and ThIr₃ compounds are 4.91 K and 5.01 K, respectively. We have compared and contrasted all the physical properties of XIr₃ (X = La, Th) compounds in this study.