Author Topic: About the relation between Paritition and LnPartition for NH3  (Read 157 times)

w_wonder

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About the relation between Paritition and LnPartition for NH3
« on: November 08, 2022, 09:53:53 PM »
From https://github.com/iRASPA/RASPA2/blob/master/examples/Tutorial/ReactionEnsembleAmmonia/simulation.input

"

Component 2 MoleculeName NH3 

 

 MoleculeDefinition Local 

 

 LnPartitionFunction 253.69"


 From

https://github.com/iRASPA/RASPA2/issues/4 and
https://github.com/iRASPA/RASPA2/files/3927153/RASPA.Ammonia.Synthesis.Partition.Function.pdf

Table 2,
"NH3 1.8118E+02 1.9951E+02 1.1422E+00 4020.5 1.66002E+08 1.498133E+08"

The partition function seems to be ~ 1*10^8. I calculated the partition function of NH3 using quantum chemistry software and got ~ 10^8 value.


 I am unable to relate 253.69 to ~1*10^8, for example, from https://www.rapidtables.com/calc/math/Ln_Calc.html

ln(1.498133e8) gives me ~ 18.82.

 May I know how the partition function and LnPartitionFunction are related? Thanks

David Dubbeldam

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Re: About the relation between Paritition and LnPartition for NH3
« Reply #1 on: November 22, 2022, 10:32:28 AM »
These value come from: https://pubs.acs.org/doi/suppl/10.1021/acs.jctc.7b00092/suppl_file/ct7b00092_si_001.pdf
and to reduce under/overflow you input them as the log of these numbers in Table S3.

w_wonder

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Re: About the relation between Paritition and LnPartition for NH3
« Reply #2 on: November 23, 2022, 12:13:59 AM »
Thanks a lot. Sorry I am still confused  :'(

Would you provide any page number for McQuarrie8 used in Table S3 and/or calculation steps? Molecular thermal wavelength from https://en.wikipedia.org/wiki/Thermal_de_Broglie_wavelength is about 10^-11 m ~ 0.1 angstrom at 298K. q/\Lambda^3 ~ q/0.1^3 is unlikely to provide 10^100 for NH3, even varying mass and temperature.

David Dubbeldam

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For a detailed explanation see:
https://homepage.tudelft.nl/v9k6y/thesis-Rahbari.pdf
Page 262 and following, and see Table  A5.