TD-DFT geometry optimization using IEFPCM solvation model

Questions
#1

Hi,
I am trying to optimize the S₁ geometry of C151 using the IEFPCM solvation model, but I am encountering an error during the calculation[Unable to diagonalize A-B
]. Could someone please help me troubleshoot this issue? I’m attaching both the input and output files below for reference.
$molecule
0 1
H 0.0000000 2.2639916 1.5669971
C 0.0000000 1.1841889 1.4710001
C 0.0000000 0.6132854 0.2132230
C 0.0000000 -0.7750478 0.0065628
C 0.0000000 -1.5912612 1.1561036
H 0.0000000 -2.6690013 1.0499500
C 0.0000000 -1.0485045 2.4156902
H 0.0000000 -1.6945226 3.2872270
C 0.0000000 0.3568676 2.6021426
O 0.0000000 1.4821708 -0.8437875
C 0.0000000 1.0720709 -2.1510077
C 0.0000000 -0.3583733 -2.3863978
C 0.0000000 -1.2287736 -1.3561831
O 0.0000000 1.9292295 -3.0076616
C 0.0000000 -2.7077190 -1.6432927
N 0.0000000 0.8817752 3.8503895
H 0.0000000 -0.6804428 -3.4181770
F 0.0000000 -2.9758235 -2.9538299
F -1.0809066 -3.3033424 -1.1100291
F 1.0809066 -3.3033424 -1.1100291
H 0.0000000 0.2862910 4.6621571
H 0.0000000 1.8781889 3.9933858
$end

$rem
BASIS = 6-31G(d,p)
GUI = 2
JOB_TYPE = Optimization
METHOD = CAMB3LYP
GEOM_OPT_MAX_CYCLES = 200
SCF_MAX_CYCLES = 500
SCF_CONVERGENCE = 8
SOLVENT_METHOD = PCM
SVP_PATH = TRUE
RPA = TRUE
CIS_N_ROOTS = 3
CIS_SINGLETS = TRUE
CIS_TRIPLETS = FALSE
CIS_STATE_DERIV = 1
MAX_CIS_CYCLES = 300
SYMMETRY = FALSE
SYM_IGNORE = TRUE
MEM_TOTAL = 248000
MEM_STATIC = 4000

$end

$pcm
THEORY IEFPCM
Heavypoints 590
method swig
radii bondi
solver inversion
$end

$solvent
DIELECTRIC 35.688
OPTICALDIELECTRIC 1.8068
$end

@@@

$molecule
read
$end

$rem
BASIS = 6-31G(d,p)
GUI = 2
JOB_TYPE = Frequency
METHOD = CAMB3LYP
SCF_CONVERGENCE = 8
SCF_MAX_CYCLES = 500
SOLVENT_METHOD = PCM
SVP_PATH = TRUE
RPA = TRUE
CIS_N_ROOTS = 3
CIS_SINGLETS = TRUE
CIS_TRIPLETS = FALSE
CIS_STATE_DERIV = 1
MAX_CIS_CYCLES = 300
SYMMETRY = FALSE
SYM_IGNORE = TRUE
MEM_TOTAL = 248000
MEM_STATIC = 4000
XC_GRID = 2
$end

$pcm
THEORY IEFPCM
Heavypoints 590
method swig
radii bondi
solver inversion
$end

$solvent
DIELECTRIC 35.688
OPTICALDIELECTRIC 1.8068
$end

#2

It’s probably a TDDFT problem rather than a PCM problem. Usually it means that the ground state has a triplet instability, which means that A-B is no longer positive definite and the solver can’t handle that. Try using the Tamm-Dancoff approximation by turning off RPA=TRUE.

I would also suggest that
(1) For geometry optimizations you can turn down the number of PCM discretization points. Default values are fine or you could even go a bit looser than that.
(2) There’s no reason to use IEF-PCM here, results for dielectric 36 will be identical with C-PCM .