Phonon dispersion relation of uranium nitrate above and below the Neel temperature
Neutron coherent inelastic scattering measurements have been made of the phonon dispersion relation of uranium nitride both above and below the Neel temperature T/sub N/ = 50 K. Within the precision of the measurements, about 1% in frequency and 10% in line width and in scattered neutron intensity, no significant changes in these phonon properties were observed as a function of temperature other than those arising from population factor changes and a small stiffening of the lattice as the temperature decreases. At 4.2 K, two acoustic and two optic branches have been determined for each of the (001), (110) and (111) directions. The optic mode measurements revealed (a) a 20% variation in frequency across the Brillouin zone and (b) an interesting disposition of the LO and TO modes, such that nu/sub LO/ > nu/sub TO/ along (001) and (110), while the reverse is true along the (111) directions. Within the experimental resolution, the LO and TO modes are degenerate near q = 0. We have been unable to obtain any satisfactory description of these results on the basis of conventional theoretical treatments (e.g. rigid-ion or shell models). Other possible interpretations of the results are discussed.
- Research Organization:
- Argonne National Lab., Ill. (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 5121966
- Report Number(s):
- CONF-770913-7; TRN: 78-009793
- Resource Relation:
- Conference: International conference on lattice dynamics, Paris, France, 5 Sep 1977
- Country of Publication:
- United States
- Language:
- English
Similar Records
Lattice dynamics of hcp Hf
Temperature dependence of the normal vibrational modes of hcp Zr
Related Subjects
URANIUM NITRIDES
DISPERSION RELATIONS
CRYSTAL STRUCTURE
INELASTIC SCATTERING
NEEL TEMPERATURE
NEUTRON DIFFRACTION
NEUTRONS
PHONONS
ULTRALOW TEMPERATURE
ACTINIDE COMPOUNDS
BARYONS
COHERENT SCATTERING
DIFFRACTION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
NITRIDES
NITROGEN COMPOUNDS
NUCLEONS
PHYSICAL PROPERTIES
PNICTIDES
QUASI PARTICLES
SCATTERING
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
URANIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies