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fevangelista / wicked

A Wick theorem kernel written in C++ and interfaced with Python
MIT License
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Support for mixed fermion/fermion spaces #7

Open shivupa opened 2 years ago

shivupa commented 2 years ago

Very similar to #6 (feel free to merge the issues if desired), is it possible to create mixed fermion/fermion spaces?

I tried to modify the coupled cluster example to reproduce the equations in https://doi.org/10.1021/acs.jctc.8b01120 but partitioning the space into separate occupied and virtual spaces isn't correct because these spaces are still related to the electron vacuum |0e> rather than a |0e0p>

Please let me know if I just missed something if this already possible.

Also thank you for the clear tutorial and examples. I played around with some of the other similar libraries and this is one of the easiest to use.

fevangelista commented 1 year ago

@shivupa: Thank you for your interest. Can you send me your setup for generating just one term so that I can investigate what is wrong? I have not tried to generate code for multiple fermionic spaces so it's possible there is something missing. One aspect that should probably be generalized is being able to request diagrams with a well defined number of hole/particle for each fermionic sector. Right now Wick&d will just count the total number of fermionic modes.

shivupa commented 1 year ago

hi @fevangelista , Thanks!

I had ended up making progress on this. I was just doing this educate myself so I had only tried to reproduce the NEO-CCSD energy expression.I cleaned up my notebook and placed it here for posterity's sake.

One aspect that should probably be generalized is being able to request diagrams with a well defined number of hole/particle for each fermionic sector. Right now Wick&d will just count the total number of fermionic modes.

It seemed what would be useful is if we could do V_ep = w.utils.gen_op('v',2,'ov','pb',exchange=False) or something along those lines?