How to read a already generated Wavefunction from .wfn file



I am still new to Psi4, but i would like to use it as a tool to generate cubes and maybe an fchk file, i already know how to do calculations and pass the wfn resulting from energy() to the fchk() function, but i would also be interested to read an .wfn file i got from a QM/MM calculation. is it possible to read the file and pass it to tee variable wfn to use in


Or is it possible to repeat the QM/MM calculation in psi4? it would be easier then, because all the other parameters are then known to psi4, like what has been done, which basis set was employed etc. I also did calculations using COSMO solvation, is there anything similar i could use to redo the calculations in Psi4?

Maybe someone has the patience to help me with my problem, it would be awesome if that was possibel to handle somehow.

Thanks for your help,


I do not believe it is currently possible to read in a fchk file. Perhaps @andysim has more input.


Correct, we can’t read the fchk files at the moment; they’re just generated internally from the wavefunction object to interface to external analysis codes that require them. Psi4 can compute QM/MM energies if you’re just looking to run a QM molecule embedded in point charges.


2019 update: one can use the psi4.core.Wavefunction.to_file() and psi4.core.Wavefunction.from_file() to achieve a similar result.