The physical and superconducting properties of hexagonal YGa2 and YB2 : A comparative ab-initio study

This study explores the properties of AlB2-type YB2 and YGa2 compounds through ab initio density-functional calculations, focusing on elastic constants, electronic structures, mechanical behavior, thermodynamic characteristics, phononic properties, and electron-phonon (e-ph) coupling. The results obtained are consistent with theoretical predictions and compare the properties of the compounds to MgB2, aiming to evaluate their potential for achieving higher critical transition temperature (Tc). YGa2 is characterized by larger structural dimensions but exhibits lower phonon frequencies due to the higher atomic mass of gallium. In contrast, YB2 shows a higher Tc (5.6 K), attributed to its stronger e-ph coupling and higher density of states at the Fermi level. The shorter B-B bond lengths in YB2 enhance its band structure and elevate the Fermi energy. Both compounds exhibit mechanical stability, with YB2 displaying greater shear resistance and stronger covalent bonding. Furthermore, YB2 possesses a higher Debye temperature (779.75 K) and greater sound velocities, indicative of superior mechanical properties. The findings highlight the potential of YB2 for superconductivity, supported by its favorable electron-phonon interactions compared to YGa2.