Dear users and developers.
I want to compute excitation energies for an organic chromophore in the presence of Rydberg orbitals.
The Rydberg basis is to be centred on the charge centroid of the molecule. So I must place there a dummy
(or a ghost atom?), and then assign to it a set of Rydberg basis functions.
My question is then: how can one specify a dummy centre in Psi4?
You can add dummy atoms as described here: http://www.psicode.org/psi4manual/1.2/psithonmol.html#ghost-atoms
For your Rydberg basis, I would add a ghosted atom of a type that isn’t present in your molecule (I’ll use He) and then define a custom basis for that atom.
assign he my-made-up-basis
[ my-made-up-basis ]
S 3 1.00
h 0.0 0.0 0.0
h 0.0 0.0 1.0
gh(he) 0.0 0.0 2.0
I hope this helps.
I have just managed to do it.