Very often, when using relativistic Fock-Space CC method to model potential energy curves (PECs) of diatomics, I notice that the calculation diverges at the dissociation distance of the two interacting atoms, in particular when, at short range, the atoms form a chemically-bonded molecule. Is there a trick to push FS-CC calculations to the dissociation region of the PEC without divergence of the energy calculation in the FS sectors?

I thank you for your time.

Best regards,

Giorgio Visentin