First-principles study of structural, electronic and elastic properties of Nb4AlC3

Using First-principles calculations, we have studied the structural, electronic and elastic properties of Nb4AlC3, a new compound belonging to the MAX phases. Geometrical optimization of the unit cell is in good agreement with the experimental data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the c-axis than along the a-axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure. The band structure shows that this compound is electrical conductor. The analysis of the site and momentum projected densities shows that bonding is due to Nb d-C p and Nb d-Al p hybridizations. The Nb d-C p bond is lower in energy and stiffer than Nb d-Al p bond. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus and Poisson's ratio for ideal polycrystalline Nb4AlC3 aggregate. We estimated the Debye temperature of Nb4AlC3 from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Nb4AlC3 compound, and it still awaits experimental confirmation.