Volume and temperature dependence of the Raman spectrum in phase II of solid CH/sub 4/

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · J. Chem. Phys.; (United States)

OSTI ID:5258425

Medina, F D

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. We conclude 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 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 59 cm/sup -1/.

• Research Organization: Department of Physics, Northeastern University, Boston, Massachusetts 02115
• OSTI ID: 5258425
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 73:1; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALKANES
CRYOGENIC FLUIDS
FLUIDS
HYDROCARBONS
LINE WIDTHS
METHANE
ORDER-DISORDER TRANSFORMATIONS
ORGANIC COMPOUNDS
ORIENTATION
PHASE TRANSFORMATIONS
RAMAN SPECTRA
SOLIDS
SPECTRA
TEMPERATURE DEPENDENCE