The electronic and mechanical properties of Fe16N2 up to 150 GPa: First-principles calculation

The electronic and mechanical properties of a tetragonal Fe–N binary compound have been investigated under extreme pressure using density functional theory with the generalized gradient approximation. The results of formation enthalpy, phonon dispersion, and elastic stability criterion show that an Fe–N binary compound is stable up to 150 GPa. On the one hand, the electronic properties of Fe16N2 have been demonstrated by the band structures and density of states. On the other hand, the elastic constants, shear, and compressional modulus derived from elastic constants impact on compressional velocity (Vp) greatly. The shear modulus of a binary compound with N is about 14.7% lower than the data of pure Fe. The density and Vp of an Fe–N binary compound, which are closer with the value of a preliminary reference earth model (PREM), are lower than the pure Fe's, especially in the part of higher pressure. In addition, the density of an Fe–N binary compound is about 5.3% lower than the Fe's. The effect of the temperature is not considered in this work, but the varying tendency indicates that the light element N incorporating in pure Fe is helpful for building an earth's core model.