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https://hdl.handle.net/2142/18843
Description
Title
Thermoelastic and dynamical properties of C2F6
Author(s)
Zeng, Shu-Xiang
Issue Date
1996
Doctoral Committee Chair(s)
Simmons, R.O.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
C2F6
Thermoelasticity
dynamical properties
neutron scattering
diffraction patters
momentum distributions
molecular orientational disorder
Language
en
Abstract
Neutron scattering and diffraction were used to measure momentum distributions
of carbon and fluorine atoms and diffraction patterns of solid C2F6 from 20 K up to its
melting point of 173.3 K, and the momentum distributions of carbon and fluorine in liquid C2F6 at 180 K. At high temperatures, heavy diffuse scattering indicates much molecular orientational disorder. On cooling, a structural phase transformation from bee crystal to triclinic crystal was verified at 103 K. The mean square momentum of fluorine atoms
increases with temperature in the lower temperature solid phase but shows little
temperature dependence in the higher temperature solid phase, with no significant change below and above the melting temperature. X-ray diffraction was used to measure
temperature dependence of lattice parameter for the bee solid and to characterize
crystalline perfection. A measurement of longitudinal elastic wave velocity in the bee
phase was made, and a set of thermoelastic properties, including longitudinal and
transverse velocities of sound, adiabatic and isothermal compressibility, elastic Debye
temperature, Grtineisen parameter, heat capacity at constant volume, intramolecular and librational components of heat capacity were calculated for a range of temperatures for the bee phase. Comparisons of the data to a model with hindered rotation of the molecules
were made. Many C2F6 properties were found to be similar to those of SF6.
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