DFT study of the crystal structure, elastic and electronic properties of the phases: Ti2InC(1-x)Nx superconductor

A systematic study was conducted to investigate the effect of substituting C by N on the crystal structure and elastic electronic properties in the Ti2InC(1-x)Nx phases using the DFT framework implemented in the CASTEP code. Initially, the crystalline structure was stabilized by geometric optimization of the Ti2InC(1-x)Nx phases. The structural properties showed that the lattice parameters a and c and, consequently, the volume decreased because of the difference between the ionic radius of C and N. According to Born's structural stability criterion, the phases with a hexagonal structure are stable for all the ranges of N content studied. Analysis of mechanical moduli shows an increase between 0.00 < x < 0.25 and a decrease for x > 0.50 in Young's modulus. At the same time, the Pugh and Poisson ratios show the phases are brittle between 0.00 < x < 0.75, ductile for x = 1.00, and all metallic, respectively. Electronic band structure calculations confirm this metallic behavior, supported by the DOS analysis. Finally, as expected, the PDOS shows an increase in the electronic states of the 2p-C (N) orbitals because of the substitution of C for N. Consequently, the density of states at the Fermi level N(E-F = 0) increases as the N content rises. Finally, using the Frolich model, we observe an increase in T-c as the N content increases; as a result, the electron-phonon coupling constant values increase from 0.51 to 0.62; these values imply the phases are moderately coupled superconductors.