First-principles pressure-dependent investigation of the physical and superconducting properties of ThCr ₂ Si ₂ -type superconductors SrPd ₂ X ₂ (X = P, As)

The physical and superconducting characteristics of SrPd₂P₂ and SrPd₂As₂ compounds with applied pressure were calculated using density functional theory. The pressure effect on the structural properties of these compounds was investigated. The results show that both lattice constants and volume decrease almost linearly with increasing pressure. The elastic constants (<i>C</i> _ij) for both compounds increase with increasing pressure and satisfy Born criteria for mechanical stability. The elastic parameters indicate the ductile behaviour and anisotropic nature of these compounds under applied pressure. The Debye temperature (<i>ϴ</i> _D) and melting temperature (<i>T</i> _m) increase with increasing pressure. The electronic band structure calculation of both compounds exhibits metallic characteristics at different pressures. The density of electronic states at the Fermi level, <i>N</i>(<i>E</i> _F), consistently decreases as pressure increases, which is also reflected in the repulsive Coulomb pseudopotential (<i>µ*</i>), and the electron-phonon coupling constant (<i>λ</i>). These optical features suggest that both compounds are suitable for optoelectronic device applications. Furthermore, the superconducting transition temperature, <i>T</i> _c, for both compounds is predicted to vary with applied pressure due to changes in <i>ϴ</i> _D <i>, N</i>(<i>E</i> _F)<i>, µ*</i> and <i>λ</i>.