Phonon dispersion in uranium measured using inelastic x-ray scattering

Phonon-dispersion curves were obtained from inelastic x-ray scattering measurements on high-purity uranium single crystals at room temperature. Modes displacing atoms along [00zeta] and propagating in all three high-symmetry directions were measured. Whereas the acoustic modes agree with the neutron measurements, the longitudinal-optic branch is about 10% higher in energy, but consistent with higher cutoff energies observed in phonon density-of-states measurements on polycrystals. The application of this x-ray technique, which requires only very small samples, opens possibilities in actinide science.