Phonon dispersion relation of uranium nitrate above and below the Neel temperature

Conference · Sat Jan 01 04:00:00 EST 1977

OSTI ID:5121966

Dolling, G; Holden, T M; Evensson, E C; Buyers, W J.L.; Lander, G H

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-31109-ENG-38
• OSTI ID: 5121966
• Report Number(s): CONF-770913-7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ACTINIDE COMPOUNDS
BARYONS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
DISPERSION RELATIONS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INELASTIC SCATTERING
NEEL TEMPERATURE
NEUTRON DIFFRACTION
NEUTRONS
NITRIDES
NITROGEN COMPOUNDS
NUCLEONS
PHONONS
PHYSICAL PROPERTIES
PNICTIDES
QUASI PARTICLES
SCATTERING
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
ULTRALOW TEMPERATURE
URANIUM COMPOUNDS
URANIUM NITRIDES