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 Title: Thermoelastic and dynamical properties of perfluoroethane Author(s): Zeng, Shu-Xiang Doctoral Committee Chair(s): Simmons, R.O. Department / Program: Chemistry, PhysicalPhysics, MolecularPhysics, Condensed Matter Discipline: Chemistry, PhysicalPhysics, MolecularPhysics, Condensed Matter Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Chemistry, Physical Physics, Molecular Physics, Condensed Matter 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$\sb6$. Issue Date: 1996 Type: Text Language: English URI: http://hdl.handle.net/2142/23770 ISBN: 9780591199819 Rights Information: Copyright 1996 Zeng, Shu-Xiang Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9712499 OCLC Identifier: (UMI)AAI9712499
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