Following the remark in the manual, saying:

" Potential scans with JOBTYPE = PES_SCAN are available for ground-state potential energy surfaces only, although one may compute excitation energies along the scanned coordinate(s) by including appropriate keywords for vertical excitation in the *$rem* section, *e.g.* , CIS_N_ROOTS for CIS/TDDFT excited states."

I am trying to do just that - perform a relaxed potential energy scan at the ground electronic state, which at each converged point is supplemented by a single point caculations of the vertical excitation energies (at the TDDFT level of theory). One may do it by hand, first obtaining the relaxed ground state geometries and compute TDDFT for each of them separately, but it is a tedious job and it seems pretty easy to be performed by the program, as the manual hints it should do.

## Unfortunately, this does not seem to work. The input looks like this:

$molecule

0 1

C 2.413597 -0.441168 1.147203

C 1.749464 0.013992 0.008578

C 2.491228 0.321590 -1.132347

C 3.871460 0.165029 -1.137171

C 4.526611 -0.290628 0.001453

C 3.794694 -0.589828 1.144740

C 0.272810 0.152503 0.009765

C -0.552931 -0.929936 0.251028

C -1.968441 -0.722871 0.237591

N -2.599378 0.408392 0.017379

C -1.800095 1.475322 -0.217541

C -0.359907 1.399838 -0.231161

C -0.396269 -2.338853 0.500151

N -1.576510 -2.902677 0.629399

N -2.531317 -1.937495 0.480104

C -2.415404 2.730734 -0.459629

C -1.666003 3.850049 -0.691850

C -0.253265 3.782525 -0.691196

C 0.377948 2.591150 -0.465647

C 0.852716 -3.144777 0.600262

C -3.933569 -2.265668 0.546017

H -3.495769 2.765343 -0.449803

H -2.154570 4.798150 -0.872905

H 0.326492 4.678401 -0.865765

H 1.457007 2.542455 -0.457966

H 1.981062 0.675621 -2.017867

H 4.434663 0.398774 -2.030459

H 5.601390 -0.410382 -0.002038

H 4.298308 -0.940433 2.035389

H 1.843031 -0.674902 2.035815

H 0.600212 -4.200895 0.667987

H 1.492811 -2.986498 -0.268251

H 1.436993 -2.867395 1.478384

H -4.176206 -2.701401 1.514648

H -4.494407 -1.345148 0.410257

H -4.198496 -2.972447 -0.240246

$end

$rem

jobtype pes_scan

method b3lyp5

dft_d d3_bj

dft_d3_s6 100000

dft_d3_s8 198890

dft_d3_a1 39810

dft_d3_a2 442110

basis def2-tzvpp

MAX_SCF_CYCLES 500

SCF_CONVERGENCE 9

scf_final_print true

MEM_STATIC 2000

MEM_TOTAL 80000

solvent_method pcm

CIS_N_ROOTS 1

CIS_TRIPLETS false

CIS_RELAXED_DENSITY true

RPA 2

$end

$pcm

Theory iefpcm

NonEquilibrium

StateSpecific perturb

$end

$solvent

solventname cyclohexane

$end

##
$scan

tors 8 7 2 1 80 120 3

$end

and the claculations crash after completing TDDFT, with a message:

Calculating analytic gradient of the CIS energy

Q-Chem fatal error occurred in module libmdc/newfileman.C, line 376:

FileMan error: Error positioning pointer with offset 18446744073708642688 in file FILE_CIS_DENSITY

Path: /net/ascratch/people/plgjoannaz/slurm_jobdir/8454306/tmp/qchem3691991/74.0

which in my opinion suggests that the program started to calculate gradients for the excited state, instead of the ground state, as intended.

Please, point me at what I am doing wrong, or whether Qchem can do such a thing that I have described, or I misunderstood the manual and it is simply impossible.

Yours!

Marcin Andrzejak