Ab Initio Investigation of Nitride in Comparison with Carbide Phase of Superconducting InX (X = C, N)

The structural, elastic, electronic, thermal, and optical properties of superconducting nanolaminates Ti 2 In X ( X  = C, N) are investigated by density functional theory (DFT). The results obtained from the least studied nitride phase are discussed in comparison with those of carbide phase having value half as that of the former. The carbide phase is found to be brittle in nature, while the nitride phase is less brittle. Elastic anisotropy demonstrates that the c -axis is stiffer in Ti 2 InN than in Ti 2 InC. The band structure and density of states show that these phases are conductors, with contribution predominantly from the Ti 3 d states. The bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient are obtained as a function of temperature and pressure for the first time through the quasiharmonic Debye model with phononic effects. The estimated values of electron-phonon coupling constants imply that Ti 2 InC and Ti 2 InN are moderately coupled superconductors. The calculated thermal expansion coefficient is in fair agreement with the only available measured value for Ti 2 InC. Further the first time calculated optical functions reveal that the reflectivity is high in the IR-visible-UV region up to  ~ 10 eV and 12.8 eV for Ti 2 InC and Ti 2 InN, respectively, showing these to be promising coating materials.