Problem Description
I got this error when I tried to convert my RMG mechanism to a Cantera yaml:
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CanteraError thrown by addReactions:
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CanteraError thrown by PlogRate::validate:
Invalid rate coefficient for reaction 'CH2CHOO(58) <=> CH3(35) + CO2(7)'
at P = 1.0132e+07, T = 500.0
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The reaction CH2CHOO = CO2 + CH3 has a negative rate at T=500K and P=100atm.
It's part of the Klippenstein_Glarborg2016 reaction library:
https://github.com/sevyharris/RMG-database/blob/e883a4c47eb25fac07510888dab1e861bd314b94/input/kinetics/libraries/Klippenstein_Glarborg2016/reactions.py#L10490
but originates from this 2015 paper: https://pubs.acs.org/doi/10.1021/acs.jpca.5b01088.
I don't see any errors in copying the parameters, but the MAE is pretty large for this range.
CH2CHOO=CO2+CH3 6.03E-03 3.46 17420.0
PLOG/1.000E-02 5.09E+33 -7.95 31290.0/
PLOG/1.000E-02 4.20E+122 -39.75 43640.0/ ! fit btw. 400 and 1250 K with MAE of 1.5%, 4.0%
PLOG/1.000E-01 1.21E+118 -33.13 73790.0/
PLOG/1.000E-01 1.96E+29 -6.29 30920.0/ ! fit btw. 400 and 1350 K with MAE of 0.4%, 1.1%
PLOG/3.160E-01 8.56E+32 -7.21 33550.0/
PLOG/3.160E-01 5.10E-66 21.37 -11110.0/ ! fit btw. 400 and 1450 K with MAE of 1.2%, 3.4%
PLOG/1.000E+00 3.27E+33 -7.22 34990.0/
PLOG/1.000E+00 1.76E-47 15.85 -5283.0/ ! fit btw. 400 and 1550 K with MAE of 0.9%, 3.6%
PLOG/3.160E+00 3.49E-79 25.01 -21020.0/
PLOG/3.160E+00 3.82E+32 -6.80 35690.0/ ! fit btw. 550 and 1650 K with MAE of 0.9%, 3.9%
PLOG/1.000E+01 8.16E+32 -6.76 37270.0/
PLOG/1.000E+01 4.62E+00 2.10 17170.0/ ! fit btw. 450 and 1750 K with MAE of 1.8%, 7.5%
PLOG/3.160E+01 7.01E+37 -8.06 42200.0/
PLOG/3.160E+01 3.49E+14 -1.58 26470.0/ ! fit btw. 500 and 1900 K with MAE of 2.2%, 10.5%
PLOG/1.000E+02 -2.51E+03 1.41 14420.0/
PLOG/1.000E+02 4.05E-09 5.14 10480.0/ ! fit btw. 400 and 2100 K with MAE of 40.7%, 150.7%
Question
I'm wondering what the best course of action is here. For my particular mechanism, I'm tempted to delete the 100atm parameters since I don't need that high of pressure anyways. That seems easier than trying to suppress the downstream Cantera errors.
But what about for the RMG library? I don't know if Franklin still has the data, but I imagine refitting the parameters with a constraint that the rate never be negative would be extremely involved. Would it be easier to comment out the last two lines with a note about the negative rate at ~500K and 100atm? Or what if we do a fit of the fit? Take the current plot at 100atm and fit a new Plog that never goes negative?
Problem Description
I got this error when I tried to convert my RMG mechanism to a Cantera yaml:
The reaction CH2CHOO = CO2 + CH3 has a negative rate at T=500K and P=100atm.
It's part of the Klippenstein_Glarborg2016 reaction library:
https://github.com/sevyharris/RMG-database/blob/e883a4c47eb25fac07510888dab1e861bd314b94/input/kinetics/libraries/Klippenstein_Glarborg2016/reactions.py#L10490
but originates from this 2015 paper: https://pubs.acs.org/doi/10.1021/acs.jpca.5b01088.
I don't see any errors in copying the parameters, but the MAE is pretty large for this range.
Question
I'm wondering what the best course of action is here. For my particular mechanism, I'm tempted to delete the 100atm parameters since I don't need that high of pressure anyways. That seems easier than trying to suppress the downstream Cantera errors.
But what about for the RMG library? I don't know if Franklin still has the data, but I imagine refitting the parameters with a constraint that the rate never be negative would be extremely involved. Would it be easier to comment out the last two lines with a note about the negative rate at ~500K and 100atm? Or what if we do a fit of the fit? Take the current plot at 100atm and fit a new Plog that never goes negative?