Heat capacity of. cap alpha. -ce between 0. 3 and 20K at pressures to 9. Okbar and magnetic fields to 7. 5T
The heat capacity of ..cap alpha..-cerium was measured at pressures from 2.3 to 9.0kbar for temperatures 0.3 to 20K and at 5.2kbar for temperatures of 1.3 to 4.2K in magnetic fields to 7.5T. The volume dependences of the electronic specific heat coefficient, ..gamma.., and the Debye temperature were determined. The volume dependence of ..gamma.. is well described by several promotional models for the cerium ..gamma..-..cap alpha.. phase transition. Agreement with band-structure calculations is obtained only by assuming a volume dependent spin-fluctuation enhancement, lambda/sub sf/, to the electron effective mass. The same lambda/sub sf/, which decreases with volume, could explain the volume dependence of the superconducting transition temperature in ..cap alpha..-cerium. The thermal expansion coefficient, ..beta.. = V/sup -1/ (dV/dT)p, was calculated from the pressure dependence of the entropy for 0.3 to 20K. The design and operation of a microcomputer based low-temperature calorimetry system is described. The system features interactive data acquisition and on-line data reduction. In addition to increased experimental efficiency, improvements in the precision of heat capacity were obtained. The heat capacity, C/sub v/, of a teflon sample was measured at pressures from 0.3 to 5.2 kbar for temperatures 0.7 to 20K. The pressure dependence of C/sub v/, is large and varies strongly with temperature. The data are well described by a Tarasov term plus two Einstein heat capacity functions. The Einstein terms involve only a small fraction of the total number of vibrational modes, but account for more than 50 percent of the pressure dependence of C/sub v/. On the basis of the data reported here and literature data for other amorphous organic polymers, it is concluded that vibrations associated with side groups are not responsible for the Einstein contributions to C/sub v/.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5322828
- Report Number(s):
- LBL-13645; ON: DE82016941
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALORIMETRY
AUTOMATION
CERIUM
SPECIFIC HEAT
TEFLON
DATA ACQUISITION
DESIGN
EXPERIMENTAL DATA
LOW TEMPERATURE
MICROPROCESSORS
ON-LINE MEASUREMENT SYSTEMS
PRESSURE DEPENDENCE
ULTRALOW TEMPERATURE
VERY HIGH PRESSURE
COMPUTERS
DATA
ELECTRONIC CIRCUITS
ELEMENTS
FLUORINATED ALIPHATIC HYDROCARBONS
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
MATERIALS
METALS
MICROELECTRONIC CIRCUITS
NUMERICAL DATA
ON-LINE SYSTEMS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHYSICAL PROPERTIES
PLASTICS
POLYETHYLENES
POLYMERS
POLYOLEFINS
POLYTETRAFLUOROETHYLENE
RARE EARTHS
SYNTHETIC MATERIALS
THERMODYNAMIC PROPERTIES
360104* - Metals & Alloys- Physical Properties
360404 - Materials- Polymers & Plastics- Physical Properties- (-1987)