Phonon Dispersion Relation for Iron

The room-temperature phonon dispersion relation of $\alpha$-Fe has been measured by using the neutron-inelastic-scattering technique. Measurements were taken on phonon groups with their wave vectors in the principal symmetry directions. A Born-von-Kármán fifth-neighbor general-force-constant model was used to analyze the data, and the phonon distribution function was obtained from the force-constant model. We see no evidence for anomalous behavior in the phonon-dispersion curves; on the contrary, the phonon spectrum is remarkably well behaved when compared with the results of the experiments performed on other bcc transition metals (Nb, Ta, Mo, and W).