Odd behaviour in diatomic molecule (Cl2) potential energy plot

[singlet]

Sounds similar to the HF/SCF discussion in this thread:

Unexpected jumps in energies for 2nd row diatomics

Hello, I’m new to psi4 and looking forward to using the python module within jupyter notebooks for class work. Following the PsiAPI Tutorial, tried to map potential curves of 2nd row diatomics. Certain diatomics give strange results despite converging without complaints. I’ve (naively) fiddled with reference wfs, setting charge and multiplicity explicitly or letting psi4 set these, changing e_convergence, basis sets, etc. and the unexpected (to me) results are reproducible. So I’m probably m…