Phonon dispersion of transverse basal-plane modes in alkali-graphite compounds
Dispersion curves for low-frequency transverse modes propagating in the basal plane have been measured in the compounds KC/sub 8/, KC/sub 24/ and RbC/sub 24/ by means of neutron inelastic scattering. The acoustic branches show at low q a behavior ..omega../sup 2/ = Aq/sup 2/ + Bq/sup 4/ characteristic of layered materials. The optical branches are derived qualitatively from graphite-like optical branches hybridized with new alkali-like branches. In stage 2 compounds, the shear constant C/sub 44/, which can be obtained by extrapolating the acoustic branch towards q = 0, is appreciably smaller than in stage-1 compounds or in pure graphite. At low temperatures, it was noted in KC/sub 24/ that a frequency gap in the acoustic branch opens up near q = 0.6 A/sup -1/, corresponding to the Brillouin-zone boundary of the low-temperature alkali superstructure.
- Research Organization:
- Ames Lab., IA (USA); Illinois Univ., Urbana (USA). Dept. of Physics; Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC02-76ER01198
- OSTI ID:
- 5828021
- Report Number(s):
- DOE/ER/01198-1394; CONF-821185-2; ON: DE83003910
- Resource Relation:
- Conference: Materials Research Society annual meeting, Boston, MA, USA, 16 Nov 1982; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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RUBIDIUM CARBIDES
CLATHRATES
CRYSTAL LATTICES
DISPERSION RELATIONS
ELASTICITY
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GRAPHITE
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LAYERS
LOW TEMPERATURE
NEUTRON DIFFRACTION
SHEAR
ALKALI METAL COMPOUNDS
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CARBON
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CRYSTAL STRUCTURE
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ELEMENTAL MINERALS
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QUASI PARTICLES
RUBIDIUM COMPOUNDS
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