I’m trying to implement Configuration interaction calculations in psi4 (using examples given in psi4numpy). The helper_CI.py has implementation of bit-determinants, this seems to be a very efficient way to implement Slater-Condon rules to calculate one- and two- electron operators in terms of determinants. I have been trying to find a reference for this form of implementation, and found this.

Does anyone here, know a reference for the implementation of bit-determinants for CI and slater-condon rules?

I need more context: are you looking for a historical reference to cite for the idea? Are you trying to implement a production level CI code and looking for code to follow?

I’m actually implementing some TD-MCSCF methods using psi4 and have been trying to scale up my calculations to small molecules. So, I’m looking for a codebase that uses bit-determinants to follow along and also possibly for some inspiration to build up some production level code.

You can see the full CI code of the Forte plugin to Psi4 here. PySCF has their FCI implementation here.