Experimental heat capacity of solid hydrogen as a function of molar volume

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6084936

Krause, J K

Constant volume heat capacity measurements have been made on six solid hydrogen samples with low orthohydrogen concentrations. The measurements extend from approximately 1.5 K to the melting line, with molar volumes ranging from 22.787 cm/sup 3//mole to 16.193 cm/sup 3//mole. Although clustering of the ortho molecules was observed, the low temperature heat capacity anomaly due to the orthohydrogen pairs could be described quite well by the assumption of a fixed distribution. The data were corrected to obtain a lattice heat capacity which on extrapolation to T = 0 yielded Debye temperatures and a volume dependent Grueneisen parameter. A modified Mie-Grueneisen approximation was used to define a volume and temperature dependent Grueneisen parameter which was used to calculate the equation of state, P(V,T), and isothermal bulk modulus, B/sub T/(V,T), for the six isochores. An extrapolation of the equation of state to T = 0 and P = 0 by two different methods yields a molar volume which, when compared with other determinations, gives a recommended value of 23.20 +- 0.05 cm/sup 3//mole. A rapid increase in the conversion rate of orthohydrogen to parahydrogen was observed at approximately theta/sub o/12. The molar volumes along the melting curve also have been determined directly for the first time in this volume range. These results have been used to show that a low temperature Lindemann melting relation is only approximately valid for solid hydrogen to 50 K.

• Research Organization: Iowa State Univ. of Science and Technology, Ames (USA)
• OSTI ID: 6084936
• Country of Publication: United States
• Language: English

Related Subjects

657006* -- Theoretical Physics-- Statistical Physics & Thermodynamics-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DATA
DEBYE TEMPERATURE
ELEMENTS
EQUATIONS
EQUATIONS OF STATE
EXPERIMENTAL DATA
GRUENEISEN CONSTANT
HYDROGEN
INFORMATION
MOLECULES
NONMETALS
NUMERICAL DATA
PHYSICAL PROPERTIES
SOLIDS
SPECIFIC HEAT
THERMODYNAMIC PROPERTIES
VERY LOW TEMPERATURE
VOLUME