Electronic, phononic and superconducting properties of trigonal Li₂ MSi₂ (M = Ir, Rh)

Abstract

We have used ab initio density functional theory to study electronic, mechanical, phononic, and superconducting properties of Li2 MSi2 (M = Ir, Rh), which has recently been produced as a new type of transition metal–based ternary compound in the trigonal structure (Horigane et al 2019 New J. Phys. 21 093056). The calculated electronic band structure and the density of states indicate that the Li2IrSi2 and Li2RhSi2 compounds 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 ( T c μ ⋆ = 0.11 ) values of 3.29 K for Li2IrSi2 and 2.82 K for Li2RhSi2 agree well with experimental estimates.