PCM in EOM-CCSD calculations: what does it do?

I looked into sample job “ccman2_eomee_pcm.in” and noticed that both the dielectric constant and optical dielectric constant were given. I was wondering what the PCM exactly does in this calculation. Does it only affect the HF orbitals used for EOM-CCSD calculations, or does it actually capture the electronic response of the solvent with regard to the excited state in some way?

What you get is just EOM-CCSD with solvent-polarized MOs, what I called the “zeroth-order” form of the solvent response. Electronic response of the solvent (using optical dielectric constant and excited-state density to re-polarize for vertical excitation) is implemented for CIS/TDDFT and for ADC, but not for EOM-CCSD. If desired, you could use the difference between zeroth-order excitation and “ptSS” (1st-order perturbation theory treatment of the electronic response) from one of those methods as a correction to the zeroth-order EOM-CCSD excitation energies, or at least to get an idea of the magnitude of the effect.

Theory is described in Section 5.2 of this review: https://doi.org/10.1002/wcms.1519

Thanks for your help, John!

Those “nonequilibrium” PCM capabilities are also coming soon for RAS-SF CI wave functions, probably in 6.0.1 release as we weren’t quite ready to make the 6.0 check-in deadline.

A related question: for sample job 11.7 on the manual:
0 1
C 0 0 0.0
O 0 0 1.21

BASIS 6-31+G*

Theory CPCM
Method SWIG
Solver Inversion
Radii Bondi

Dielectric 78.39
OpticalDielectric 1.777849

I suppose it incorporates the response of the solvent to the excited states using the LR approach, as indicated by the line
“Adding PCM contribution to the XC response (LR-PCM)”
in the output. Here the keyword “NonEquilibrium” is not in the $pcm section, so I was wondering which dielectric constant will be used here: the dielectric or optical dielectric?

Static dielectric, 78.39 in this example