Hello everyone,
I came across an open-source code for generating PCT curves, which can be used to plot the PCT behavior for various alloys. However, while practicing with the code, I have noticed that the calculated pressure values are extremely high—on the order of 10²³—which seems physically unrealistic.
I have attached an image of the plot for reference, along with the relevant paper I have been using. I would greatly appreciate any guidance on identifying the potential source of this error and suggestions for correcting it. Please assist me with this for quite a while, haha.
Thank you very much for your time and assistance.
Best regards, Ketan Karkare
Article An open-source code to calculate pressure-composition-temper...
Ketan Karkare ,The astronomically high pressures in the plot most likely stem from sign/units/log-base mistakes in the Van’t Hoff/Sieverts relations or from using phase/thermodynamic parameters outside the model’s domain, which will exponentiate errors into values as large as 10^23 atm as seen in the attached curve. Correcting the enthalpy/entropy sign convention, enforcing Kelvin temperature and per‑mol‑H2 units, restoring the 1/2 factor from Sieverts’ law, and using the proper logarithm base typically brings plateau pressures back to realistic ranges used in PCT work.
Likely causes
- Van’t Hoff sign error: for hydride formation, the common form is lnP=ΔHRT−ΔSRlnP=RTΔH−RΔS with ΔH
Anup Mahato Thank you Anup for suggestions, for more suggestive and fruitful discussions, I have uploaded the code as well!
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