Lattice Dynamics of Holmium

The dispersion relation for the normal modes of vibration of holmium metal at room temperature has been measured by means of slow-neutron inelastic scattering techniques. Phonon frequencies for wave vectors along the principal symmetry directions have been determined and, in addition, some experimental information about the phonon frequencies along the boundaries of the Brillouin zone are reported. The data have been fitted with a Born-von K\'arm\'an force model which includes interactions out to the eighth nearest neighbor. The interactions have been assumed to be general (tensor) out to the fourth nearest neighbor and axially symmetric beyond. The model has been used to calculate a frequency distribution function g(ν), the lattice specific heat, and the corresponding Debye temperature.