Lattice Vibrations in Molybdenum

A neutron inelastic scattering study has been made of the normal modes of vibration of molybdenum in a ($1\overline{1}0$) plane at room temperature using a cold-neutron chopper time-of-flight technique. The measured frequency—wave-vector results are in general agreement with the symmetry-axis data of Woods and Chen but show further anomalous behavior in several regions in this plane. The "normal" phonons (those not in anomalous regions) are fitted acceptably by Born—von Karman general force models that include at least six neighbors with a relatively large value for the sixth-neighbor force constant. The anomalous regions appear to be examples of Kohn anomalies, and two of these are interpreted on this basis to give information on dimensions of the near-planar sections of the Lomer model of the Fermi surface.