Neutron scattering investigation of layer-bending modes in alkali-metal--graphite intercalation compounds
Phonon dispersion curves for low-frequency transverse modes propagating in the basal plane have been measured in the alkali-metal--graphite intercalation compounds KC/sub 8/, CsC/sub 8/, KC/sub 24/, and RbC/sub 24/ by means of neutron spectroscopy. The acoustic branches show an almost quadratic dispersion relation at small q, characteristic of strongly layered materials. The optical branches of stage-1 compounds can be classified as either graphitelike branches showing dispersion, or as almost dispersionless alkali-metal-like modes. Macroscopic shear constants C/sub 44/ and layer-bending moduli have been obtained for the intercalation compounds by analyzing the data in terms of a simple semicontinuum model. In stage-2 compounds, a dramatic softening of the shear constant by about a factor of 8 compared with pure graphite has been observed. Low-temperature results on KC/sub 24/ indicate the opening of a frequency gap near the alkali-metal Brillouin-zone boundary, possibly due to the formation of the alkali-metal superstructure.
- Research Organization:
- Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
- OSTI ID:
- 6527541
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 26:10
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALKALI METAL COMPOUNDS
NEUTRON SPECTROSCOPY
PHONONS
GRAPHITE
BRILLOUIN ZONES
CLATHRATES
DISPERSION RELATIONS
ELASTICITY
INELASTIC SCATTERING
LOW TEMPERATURE
CARBON
ELEMENTAL MINERALS
ELEMENTS
MECHANICAL PROPERTIES
MINERALS
NONMETALS
QUASI PARTICLES
SCATTERING
SPECTROSCOPY
TENSILE PROPERTIES
ZONES
360204* - Ceramics
Cermets
& Refractories- Physical Properties