Calculated Electronic Structure and Hyperfine Interactions on γ′Fe 4 Z (Z  N, C)

The spin‐polarized linear muffin‐tin orbital (LMTO) method is used to calculate the electronic energy bands of γ′‐Fe 4 Z (Z = N, C) and to study the hyperfine interactions in Fe 4 Z. In comparison with the effect of N atoms, the C atom enhances the itineracy of electrons and then in turn prevents the exchange splitting. The C atom brings about a larger charge transfer among the atoms in the unit cell. The results show that the interaction between the Z and the nearest Fe atoms (Fe II ) is stronger than that between the Z and the next‐nearest Fe atoms (Fe II ). According to the calculated Fermi contact hyperfine magnetic field ( H FC ), the proportionality constant between the core contribution of H FC and the local magnetic moment of the atom is evaluated as ≈ 13 T/μ B . The calculated values of H FC and the Mössbauer isomer shift (IS) indicate that the Fe I Fe II and FeZ interactions strongly depend on the Z atom. The results of H hf and IS are qualitatively in agreement with the experimental results.