Electronic, phononic and superconducting properties of trigonal Li₂MSi₂(M=Ir, Rh)

We have usedab initiodensity functional theory to study electronic, mechanical, phononic, and superconducting properties of Li₂MSi₂(M= Ir, Rh), which has recently been produced as a new type of transition metal-based ternary compound in the trigonal structure (Horiganeet al2019New J. Phys.21093056). The calculated electronic band structure and the density of states indicate that the Li₂IrSi₂and Li₂RhSi₂compounds are in metallic character. Mechanical properties such as elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Debye temperature were calculated for these compounds. The calculated results suggest that the compounds are mechanically stable and behave in a ductile manner. The phonon spectra have no imaginary frequency, which proves that these compounds are dynamically stable. Electron-phonon coupling parameters confirm that they are weak-coupling superconductors. Although the influence of spin-orbit coupling in superconductivity is not significant for these compounds, it has a very small influence on electronic structure for Li₂IrSi₂. The calculated critical temperature (Tcμ⋆=0.11) values of 3.29 K for Li₂IrSi₂and 2.82 K for Li₂RhSi₂agree well with experimental estimates.