Some Measurements of Phonon Dispersion Relations in Iron

The dispersion relations for phonons have been measured for symmetry directions in a crystal of iron by means of neutron spectrometry. The time-of-flight technique was employed, the experiment being carried out on the twin-rotor spectrometer at PLUTO. The dispersion curves obtained have been fitted in each case by a cosine series expansion in which the coefficients are interplanar force constants of the crystal. Interatomic force constants consistent with the experimental data have also been derived.