Thermoelastic and dynamical properties of perfluoroethane
Zeng, Shu-Xiang
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https://hdl.handle.net/2142/23770
Description
Title
Thermoelastic and dynamical properties of perfluoroethane
Author(s)
Zeng, Shu-Xiang
Issue Date
1996
Doctoral Committee Chair(s)
Simmons, R.O.
Department of Study
Chemistry, Physical
Physics, Molecular
Physics, Condensed Matter
Discipline
Chemistry, Physical
Physics, Molecular
Physics, Condensed Matter
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Physics, Molecular
Physics, Condensed Matter
Language
eng
Abstract
Neutron scattering and diffraction were used to measure momentum distributions of carbon and fluorine atoms and diffraction patterns of solid C$\sb2$F$\sb6$ from 20 K up to its melting point of 173.3 K, and the momentum distributions of carbon and fluorine in liquid C$\sb2$F$\sb6$ at 180 K. At high temperatures, heavy diffuse scattering indicates much molecular orientational disorder. On cooling, a structural phase transformation from bcc 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 bcc solid and to characterize crystalline perfection. A measurement of longitudinal elastic wave velocity in the bcc phase was made, and a set of thermoelastic properties, including longitudinal and transverse velocities of sound, adiabatic and isothermal compressibility, elastic Debye temperature, Gruneisen parameter, heat capacity at constant volume, intramolecular and librational components of heat capacity were calculated for a range of temperatures for the bcc phase. Comparisons of the data to a model with hindered rotation of the molecules were made. Many C$\sb2$F$\sb6$ properties were found to be similar to those of SF$\sb6$.
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