J/A+A/595/A130 Thermodynamic quantities of molecular hydrogen (Popovas+, 2016)
Partition functions. I. Improved partition functions and thermodynamic
quantities for normal, equilibrium, and ortho and para molecular hydrogen.
Popovas A., Jorgensen U.G.
<Astron. Astrophys. 595, A130 (2016)>
=2016A&A...595A.130P 2016A&A...595A.130P (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: miscellaneous - molecular data - astrochemistry - equation of state
Abstract:
Hydrogen is the most abundant molecule in the Universe. Its
thermodynamic quantities dominate the physical conditions in molecular
clouds, protoplanetary disks, etc. It is also of high interest in
plasma physics. Therefore thermodynamic data for molecular hydrogen
have to be as accurate as possible in a wide temperature range.
We here rigorously show the shortcomings of various simplifications
that are used to calculate the total internal partition function.
These shortcomings can lead to errors of up to 40 percent or more in
the estimated partition function. These errors carry on to
calculations of thermodynamic quantities. Therefore a more complicated
approach has to be taken.
Seven possible simplifications of various complexity are described,
together with advantages and disadvantages of direct summation of
experimental values. These were compared to what we consider the most
accurate and most complete treatment (case 8). Dunham coefficients
were determined from experimental and theoretical energy levels of a
number of electronically excited states of H2. Both equilibrium and
normal hydrogen was taken into consideration.
Description:
New partition functions for equilibrium, normal, and ortho and para
hydrogen are calculated and thermodynamic quantities are reported for
the temperature range 1-20000K. Our results are compared to
previous estimates in the literature. The calculations are not limited
to the ground electronic state, but include all bound and quasi-bound
levels of excited electronic states. Dunham coefficients of these
states of H2 are also reported. Reported internal partition functions
and thermodynamic quantities in the present work are shown to be more
accurate than previously available data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
h2equil.dat 177 20000 Partition function and thermodynamic quantities
for equilibrium H2 in 1K temperature steps,
ranging 1-20000K
h2normal.dat 177 20000 Partition function and thermodynamic quantities
for normal H2 in 1K temperature steps,
ranging 1-20000K
h2ortho.dat 177 20000 Partition function and thermodynamic quantities
for ortho-H2 in 1K temperature steps,
ranging 1-20000K
h2para.dat 177 20000 Partition function and thermodynamic quantities
for para-H2 in 1K temperature steps,
ranging 1-20000K
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Byte-by-byte Description of file: h2*.dat
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Bytes Format Units Label Explanations
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1- 7 F7.1 K T Temperature
9- 29 F21.17 --- Q Partition function
31- 52 E22.17 J Eint/RT Internal contribution to the
thermodynamic energy
54- 74 F21.14 J/mol H-H(0) Enthalpy
76- 95 F20.16 J/K.mol S Entropy
97-114 F18.15 J/K.mol Cp Constant-pressure specific heat
116-137 E22.17 J/K.mol Cv Constant-volume specific heat
139-158 E20.15 J/K.mol [-G-H(0)]/T Gibbs free energy
160-177 F18.16 --- gamma Adiabatic index
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Acknowledgements:
Andrius Popovas, popovas(at)nbi.ku.dk
StarPlan & NBI, University of Copenhagen, Denmark
(End) A. Popovas [Univ. Copenhagen, Denmark], P. Vannier [CDS] 18-Jul-2016