CCSD for core excited electrons

Questions
#1

We are trying to understand how to carry out the computations using
Q-Chem in the following paper (the paper says Q-Chem v5.4 was used)

Accurate core excitation and ionization energies from a state-specific
coupled-cluster singles and doubles approach

Juan E. Arias-Martinez, Leonardo A. Cunha, Katherine J. Oosterbaan,
Joonho Lee and Martin Head-Gordon

Accurate core excitation and ionization energies from a state-specific coupled-cluster singles and doubles approach - Physical Chemistry Chemical Physics (RSC Publishing)

Specifically the question is how to compute CCSD for a core ionized state: how to tell Q-Chem to not use the unoccupied core orbital for coupled cluster excitations?

The paper mentions that the development version 5.4 of Q-Chem was used for the mentioned calculations; we wonder if the development version might have involved custom changes; and if those changes were included in the later versions of the program.

Thank you

#2

Unfortunately, I implemented the different schemes in a legacy coupled-cluster module and it did not make it into the release versions of QChem.

#3

Thanks — that’s unfortunate indeed. Can I ask if the code might still exist and is possibly usable?

#4

I believe the code still exists and should work but I dont know what QChem’s policy wrt. old development branches is. I suppose you could submit a feature request to have it properly implemented & released? I defer to a member of the QChem team here…

#5

Thanks for clarifying. I’ll contact the QChem team, it’d be great to have that functionality in the software. We’d need this as reference for another computation.

#6

Just a quick update: I submitted the feature request at Q-Chem and they said it’s now up to you to proceed to integrate the feature into Q-Chem codebase. I hope it works out!