PCM and Detachment/attachment density

Questions
#1

Hi developers and users,
Could you kindly clarify whether the keywords for attachment-detachment density analysis is compatible with the PCM keywords?
Thank you for the assistance.

#2

I think it should be okay but let us know if you experience problems (I haven’t checked).

What you would be getting are the particle/hole densities based on MOs equilibrated to ground-state solvation effects. For something like ptSS non-equilibrium solvation, the correction is perturbative so it won’t show up in the density. State-specific solvation will show up in the density.

#3

Thank you Prof. Herbert for your time and assistance.
When I included both the keywords for state-specific PCM and attachment-detachment density in a single calculation, a fatal error occurred. Interestingly, the program runs without any issues when I omit the keywords for attachment-detachment density.
The input goes as follows:

$molecule
read opt_wat.txt
$end

$rem
METHOD wB97X-D
BASIS 6-31+G(d,p)
JOB_TYPE sp
max_scf_cycles 200
SCF_CONVERGENCE 8
THRESH 14
INCDFT FALSE
PRINT_GENERAL_BASIS TRUE
PRINT_ORBITALS 10
pcm_print 1
RPA 2
cis_singlets TRUE
cis_triplets FALSE
cis_n_roots 10
NTO_PAIRS 2
SYMMETRY_IGNORE TRUE
SYMMETRY FALSE
cis_state_deriv 10
CIS_DYNAMIC_MEM TRUE
CIS_RELAXED_DENSITY TRUE
CIS_MOMENTS TRUE
SOLVENT_METHOD PCM
TDDFT_PCM FALSE
plots TRUE
make_cube_files TRUE
$end

$pcm
Theory IEFPCM
NONEQUILIBRIUM TRUE
ChargeSeparation Pekar
StateSpecific Perturb
$end

$solvent
Dielectric 78.39
OpticalDielectric 1.78
$end

$plots
grid_points 100 100 100
attachment_detachment_density 1-5
$end

What can I do to resolve this error ?

#4

What version of Q-Chem are you running? It must be prior to 6.1.0, because the keyword TDDFT_PCM was renamed as TDDFT_LR_PCM in 6.1.0.

I am running the latest version, 6.2.1, so the behavior may not be identical but I do think you’ve found a bug, which I will report. Fortunately I think that I also found a workaround. This requires making two changes:
(1) Set RPA = 0 or RPA = 1 (i.e., don’t use 2). This will either do TDA, or else TDA then full TDDFT. Except occassionally for very large molecules there’s usually no point in setting RPA = 2 because the TDA is used as a guess for the full TDDFT.
(2) Use the old $plot format.

A minimal set of changes to your input file, which works for me, is the following:

$rem
…
RPA = 1
!plots TRUE ! turn this off
$end

$plots
you may want to change the grid
100 -10.0 10.0
100 -10.0 10.0
100 -10.0 10.0
0 0 0 5
1 2 3 4 5
$end

#5

Thank you Prof. Herbert.
Now the program is running without any error. I just set the RPA to 1 and $plots remain the same as before because with the old format $plots ,it is showing error.

If you don’t mind, could you please explain how to set up the grid for a molecule?

#6

Please see the description in the manual,
https://manual.q-chem.com/latest/sect_plot.mo.html

It also seems that your original input might work if you just set RPA=1 instead of 2. At least, it works for Q-Chem v. 6.2.1 in that case. RPA=2 does generate an error, which is a bug. It’s actually RPA=2 that’s the problem rather than the PCM.