Using Qchem files with Gaussian

Questions
#1

Hi
Is it possible to use the Qchem checkpoint(wavefunction) with Gaussian16?

Can *.fchk file from Gaussian be used for calculation in Q-chem and how?
#2

MOKIT does not seem to support that, at least from what I read here:
https://jeanwsr.gitlab.io/mokit-doc-mdbook/chap4-5.html
The Q-Chem .fchk file is human-readable ASCII so in principle if you knew Gaussian’s checkpoint format you could write a script to interconvert. Beware a re-ordering of the d,f,… functions.

#3

MOKIT has a standardize_fch function to standardize the qchem’s fchk file to make it acceptable by Gaussian. With fchk file, you can acquire Gaussian’s chk file by Gaussian’s unfchk. Feel free to open an issue if you have any question using it.

We didn’t implement a qchem2fch (“53.0 to fch”) function because we don’t need it when we have the standardized fch.

2 Likes
#4

That is helpful to know, thanks for posting.