ECP implementation in PSI4

Dear developers of Psi4,

Since commonly used ECPs in quantum chemistry are in the form of gaussian potentials, it seems to me that a minor change to can yield the matrix elements of ECP potential energy terms in AO basis. May I know if there are other problems which I did not foresee that hinder the implementation of ECPs in Psi4?



IIRC that’s only one half of the ECP implementation, you also need to handle the “non-local terms”.