Effect of N distribution on elastic and electronic properties of hexagonal ε-Fe6Nx by first-principles calculations

In this paper, the effect of N distribution on the elastic and electronic properties of hexagonal ε-Fe6Nx (x=1, 2, and 3) phases is studied by first-principles calculations. The calculated formation energies of ε-Fe6Nx phases decrease with the increasing distance between the N atoms, which demonstrates that the interaction between the interstitial N atoms is of repulsive nature. The theoretical elastic constants, bulk modulus (B), shear modulus (G), ratios of B to G, Young's modulus (E), Poisson's ratios (v) of ε-Fe6Nx phases are obtained, which are important parameters for the crystal materials and surface coatings. The more stable interstitial conifiguration enables the ε-Fe6Nx phases to possess higher B, G and E. Densities of states are given for all the configurations of ε-Fe6Nx phases to discuss the origins of the variations of energetic stability and elastic properties.