Fchk format options


Does anyone know if there are any options to adjust the data stored in the fchk file? I am using a parser that was originally written for gaussian fchk files so it expects the energies to be present in the file.

I am currently generating fchk with IQMOL_FCHK=True.

Thanks in advance for your help!

Hi Matt,

It is currently not possible to configure which fields are added to the fchk file, aside from the export of additional densities via libwfa when doing excited state calculations. There are a few options:

  1. We can add missing fields. I see at least SCF Energy and Total Energy. Is there anything else you need? This has the downside of you needing to wait for a Q-Chem release, the next of which (5.4.2) will be in early December.
  2. Rewrite this part of the parser to read from the main output file, rather than the fchk file. This has the downside that you will have to make (potentially major) modifications to the existing code. If it’s in Python, you can hook in pyQChem or cclib to read this file.

Hi Eric,

No problem! Yes I think I’ll go the rewrite parser route. It shouldn’t take too long to accomplish this. I was just hoping there was going to be a shortcut =).

If you guys are thinking of implementing fchk compatibility with Gaussian anyways, the fields supported by the parser are: iodata/fchk.py at 234ab7df57c8a141376fe83b674211b8bbe2b757 · theochem/iodata · GitHub.

Thanks for your help!

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Note also that angular momentum functions starting with L=2 (d functions) are ordered differently in Q-Chem as compared to Gaussian.