title: Large harmonic softening of the phonon density of states of uranium.
abstract: Phonon density-of-states curves were obtained from inelastic neutron scattering spectra from the three crystalline phases of uranium at temperatures from 50 to 1213 K. The alpha-phase showed an unusually large thermal softening of phonon frequencies. Analysis of the vibrational power spectrum showed that this phonon softening originates with the softening of a harmonic solid, as opposed to vibrations in anharmonic potentials. It follows that thermal excitations of electronic states are more significant thermodynamically than are the classical volume effects. For the alpha-beta and beta-gamma phase transitions, vibrational and electronic entropies were comparable.
authors: California Institute of Technology, Pasadena 91125, USA.
authors: M E
authors: ME
authors: Manley
authors: B
authors: B
authors: Fultz
authors: R J
authors: RJ
authors: McQueeney
authors: C M
authors: CM
authors: Brown
authors: W L
authors: WL
authors: Hults
authors: J L
authors: JL
authors: Smith
authors: D J
authors: DJ
authors: Thoma
authors: R
authors: R
authors: Osborn
authors: J L
authors: JL
authors: Robertson