First-principles calculations of physical properties and superconductivity of orthorhombic ScRuSi and ZrRhSi

We have performed ab initio pseudopotential calculations of the structural, electronic, elastic, mechanical, vibrational, electron-phonon interaction, and superconducting properties of ScRuSi and ZrRhSi. An assessment of their elastic and mechanical properties reveals that ScRuSi is a ductile compound, while ZrRhSi is a brittle compound. For both compounds electronic energy bands in the vicinity of the Fermi level originate from the $d$ states of transition-metal atoms. The Eliashberg spectral function reveals that low-frequency phonon modes due to coupled motions of transition-metal atoms are more involved in the process of scattering of electrons than the high-frequency modes due to the vibrations of Si atoms. The average electron-phonon coupling parameter is calculated to be 0.54 for ScRuSi and 0.84 for ZrRhSi from the integration of the Eliashberg spectral function. It is found that the relatively weaker electron-phonon interaction in ScRuSi makes its superconducting transition temperature value $({T}_c=3.23 \mathrm{K})$ considerably lower than that of ZrRhSi $({T}_c=10.45 \mathrm{K})$.