Both SCF calculations (e.g., based on MOM) and ROKS calculations can be performed with
continuum solvation effects modeled by a polarizable continuum model (PCM).
(The solvation model itself is described in Section 11.2.3.) As for the ground state,
the self-consistent PCM treatment along the SCF procedure provides equilibrium
solvation of the calculated excited state (set SOLVENT_METHOD = PCM
and include the $pcm block). During equilibrium solvation, both slow (nuclear)
and fast (electronic) solvent degrees of freedom are relaxed (governed by
Dielectric in the $solvent block), as is appropriate for long-lived states.
However, fast vertical excitation or emission occurs on a shorter timescale,
requiring the relaxation of only the fast electronic solvent polarization
(governed by Dielectric_Infi, see Section 11.2.3.3).
In Q-Chem, such nonequilibrium solvation effects can be included
to first order with a perturbative state-specific (ptSS) correction.
1420
J. Chem. Phys.
(2015),
143,
pp. 204104.
Link
,
879
J. Phys. Chem. A
(2015),
119,
pp. 5446.
Link
To begin with, a nonequilibrium SCF or ROKS calculation requires equilibrium solvation of the initial state (ground state for absorption and excited state for emission). By activating RF_ptSS_Save= true in the $pcm block, the equilibrated reaction field is then stored on disk. Setting RF_ptSS_Read = true in an arbitrary later job for the final state reads the reaction field again. This automatically triggers a frozen reaction-field (fRF) SCF with the stored reaction field of the initial state. The resulting SCF energy corresponds to a zeroth order calculation of the final state in the reaction field of the initial state. To obtain the first-order nonequilibrium result, the fast solvent polarization is relaxed for the final state by adding a perturbative ptSS correction, which is printed after the converged fRF-SCF calculation.
RF_ptSS_Save
Save the current reaction field to disk.
INPUT SECTION: $pcm
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Save the reaction field in the current job.
FALSE
Do not save the reaction field in the current job.
RECOMMENDATION:
The reaction field is saved for the reference state, which is for SCF
or ROKS just the SCF result, but for TDDFT + II-SS-PCM the chosen reference state
(see Section 7.3.5.2). Activating RF_ptSS_SAVE
for several subsequent jobs overwrites the reaction field.
RF_ptSS_Read
Read the reaction field from disk and perform a fRF-SCF + ptSS-PCM calculation with it.
INPUT SECTION: $pcm
TYPE:
BOOLEAN
DEFAULT:
FALSE
OPTIONS:
TRUE
Read the reaction field in the current job.
FALSE
Do not read the reaction field in the current job.
RECOMMENDATION:
The SCF result corresponds to zeroth order solvation of the final state.
For first-order nonequilibrium solvation add the ptSS correction
printed after the fRF-SCF.
Example 7.52 Vertical emission energy of formaldehyde in acetonitrile with ROKS + PCM and a nonequilibrium ptSS-PCM correction.
$rem jobtype sp method PBE0 basis def2-SVP scf_convergence 8 point_group_symmetry False solvent_method pcm $end $pcm theory iefpcm rf_ptss_save true ! Save the final ground state reaction field $end $solvent Dielectric 35.688000 ! Acetonitrile Dielectric_Infi 1.806874 $end $molecule 0 1 H -0.940372 0.000000 1.268098 H 0.940372 0.000000 1.268098 C 0.000000 0.000000 0.682557 O 0.000000 0.000000 -0.518752 $end @@@ $rem method PBE0 jobtype sp basis def2-SVP scf_guess read roks true unrestricted false scf_convergence 8 point_group_symmetry False solvent_method pcm $end $pcm theory iefpcm rf_ptss_read true ! Read the prior reaction field and start fRF-SCF $end $solvent Dielectric 35.688000 ! Acetonitrile Dielectric_Infi 1.806874 $end $molecule 0 1 read $end