Creating a plugin for a SCF calculation from the DePrince tutorials

I am using the DePrince tutorials to make my own SCF plugin ( However, when I run “psi4 --new-plugin myscf”, I get an error which I don’t understand or know how to fix:

/Users/tarinihardikar/psi4conda/lib/python2.7/site-packages/v2rdm_casscf/ loaded.
Traceback (most recent call last):
File “/Users/tarinihardikar/psi4conda/bin/psi4”, line 173, in
raise KeyError(“The file %s does not exist.” % args[“input”])
KeyError: ‘The file --new-plugin does not exist.’

In case it helps, I have attached an image of the installation test.



The problem is that this command has changed recently. Try:

psi4 --plugin-name myscf

instead. Thanks for pointing out the error in the tutorial.


Thank you so much!

I just had another quick question: why does the v2rdm_casscf/ site package load every time I run a psi4 command? What is this package?

Thanks again!

It’s this. Plugins always print a message when they load and v2rdm is a “perma-plugin” that will load if found. Sorry for the repeated printing. The loading can be suppressed if it’s interfering.

Thanks Lori, good to know what’s happening!

Do you or Dr. DePrince know of any tutorials or guides I could use to write a working SCF plugin that explains each step? I’m new to both quantum chemical computing and programming, so any and all help would be appreciated!

Check out the Psi4NumPy project (


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My tutorial is very similar to Daniel Crawford’s: (I based mine on his). David Sherrill has nice notes on SCF, too:

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Thank you very much!