High pressure studies to determine the effects of volume and temperature on the lattice dynamics of molecular solids: N/sub 2/, CO/sub 2/, CH/sub 4/. Progress report for period July 1, 1979 - June 30, 1980
The temperature dependence of the far infrared spectrum of ..cap alpha..-N/sub 2/ was studied for a sample at constant volume. The two modes observed near 50 and 72 cm/sup -1/ have frequencies which increase slightly with temperature. The integrated intensity of the mode near 50 cm/sup -1/ remains constant with temperature, within experimental uncertainty. The Grueneisen parameter of this mode was estimated to be approx. 3. A study of the volume dependence of the infrared spectrum of ..cap alpha..-N/sub 2/ is currently under progress. Two samples of solid CH/sub 4/ of different densities were grown. Grueneisen parameters of 2.6 and 3.1 were obtained for the librational mode and one translational mode in phase II. The former indicates an anisotropic intermolecular potential with a strong volume dependence. Changes in the spectrum indicate that the II-III phase transition involves a sudden, simultaneous tetragonal distortion of the lattice and ordering of the orientationally disordered molecules of phase II, with a slow reorientation of the ordered molecules. The librational mode of phase II does not go soft near the transition to the orientationally disordered phase I. The temperature dependence of the linewidth for this mode can be explained by a thermally activated reorientation of the ordered molecules in phase II with an activation energy of 60 cm/sup -1/.
- Research Organization:
- Northeastern Univ., Boston, MA (USA)
- DOE Contract Number:
- AC02-79ER10443
- OSTI ID:
- 5440363
- Report Number(s):
- DOE/ER/10443-1
- Country of Publication:
- United States
- Language:
- English
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High-pressure studies to determine the effects of volume and temperature on the lattice dynamics of molecular solids: N/sub 2/, CO/sub 2/, CH/sub 4/. Final report for period July 1, 1979-August 31, 1981
Orientation dynamics in white phosphorus (P{sub 4})
Related Subjects
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKANES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CRYOGENIC FLUIDS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
ELEMENTS
FLUIDS
GRUENEISEN CONSTANT
HYDROCARBONS
INFRARED SPECTRA
METALS
METHANE
NICKEL
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
RAMAN SPECTRA
RESEARCH PROGRAMS
SPECTRA
TEMPERATURE EFFECTS
TRANSITION ELEMENTS
VOLUME