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 -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 and phase transitions, vibrational and electronic entropies were comparable.
- Received 3 August 2000
DOI:https://doi.org/10.1103/PhysRevLett.86.3076
©2001 American Physical Society