Interaction and charge transfer in the iron nitride Fe4N.

The linearized augmented-plane-wave method has been used to calculate the electronic bands of the cubic iron nitride ${\mathrm{Fe}}_{4}$N. Strong interaction between N 2p and Fe 4s orbitals of nearest Fe atoms (FeII has been revealed. This interaction leads to an increase in the N 2p population. The Fe 3d bands remain almost the same as in the pure Fe metal with negligible interaction with neighboring N orbitals. However, the occupation of the FeII 3d bands and the total number of electrons of FeII atoms increases due to less screening. This unified picture clarifies the controversy in the previous explanations of the experimental results obtained from magnetic measurements, electron diffraction, and photoelectron spectroscopy.