Structural, electronic and dynamical stability of heavy metal iron pernitride: a spin polarized first-principles study

Abstract

First principles calculations using ab initio density functional theory using the ultrasoft pseudopotential method and generalized gradient approximations (GGA) have been carried out for heavy metal iron-pernitride (FeN₂). We have performed both non-spin and spin polarized calculations and found that the spin polarized ground state is energetically more favourable with a magnetic moment of 1.86 μ _B. The calculated electronic band structure, density of states and contour plot suggest that natural iron-pernitride is metallic. The high bulk modulus of FeN₂ confirms that the FeN₂ has lower compressibility and high hardness. The present values of the bulk modulus, N-N bond length, magnetic moment and optimized structure parameters agree with the previous studies. A detailed analysis of the phonon dispersion curves allows us to conclude that the spin polarized phonon dispersion curves contain positive frequencies throughout the Brillouin zone and hence confirms the dynamical stability. The eigen displacements of Raman and infrared active phonon modes at the zone centre for FeN₂ are discussed in detail. The total and partial phonon density of states are also reported along with lattice specific heat and Debye temperature.