Hello I am trying to evaluate the coupling of two simple monoatomic ions for example Ne+ and Cl- forming Ne and Cl, in my case I would like to specify the Ne at a specific excited state like 2p5_3s or 2p5_3p. Is there a trick in qchem can do this kind of operation? Thank you!
Could you please clarify what you mean by coupling? Difference in energy between the combined system and individual isolated ions? There is also ambiguity in how you’d like to define the excited states: it is possible to obtain them via TDDFT, MOM, or simple repopulation of ground state SCF orbitals.
I am sorry for the unclear description in the question, I was referring to electronic coupling between the initial and final state for a electron transfer process. I have noticed that qchem provides some features to obtain the coupling value (via direct solving for energy eigen states and etc), however I am new to the topic and the DFT software, the ultimate need is just to compute the coupling for the states that’s involved in the neutralization of two ions, but the products or neutrals do not have the electron configuration of their typical ground state, instead they are in some excited state that I usually read from NIST since they are all monoatomic species. I wonder if i can input a specific electron configuration for the product state as the starting point or the end point for qchem.
There are indeed methods for electronic (energy transfer) couplings: Q-Chem 4.3 User’s Manual : Electronic Couplings for Electron Transfer and Energy Transfer
I think that what I would try in your case to to use these methods but with a non-aufbau determinant for the fragment that is not in its ground state. Q-Chem also contains several algorithms for locating non-aufbau solutions to the SCF equations including MOM (or IMOM), STEP, and SGM.
This is sort of a non-standard calculation so I would also be on the lookout for any funny behavior.