Geometery optimization problem at SF-TDDFT

Questions
#1

I am facing a problem while optimizing the excited state using SF-TDDFT. I want to optimize 4th excited state. Here in the input
$molecule
0 3
coordinates
$end

$rem
BASIS = GEN
PURECART = 1
EXCHANGE = omegaB97X-D
omega = 156
GUI = 2
JOB_TYPE = OPTIMIZATION
MAX_CIS_CYCLES = 700
SCF_CONVERGENCE = 8
MAX_SCF_CYCLES = 700
THRESH = 14
MOM_START = 9
SPIN_FLIP = 1
CIS_N_ROOTS = 5
CIS_STATE_DERIVATIVE = 4
MEM_STATIC = 6000
MEM_TOTAL = 30000
SOLVENT_METHOD = PCM
$end

$solvent
DIELECTRIC 32.613000
OPTICALDIELECTRIC 1.765709
$end

$basis
H 0
S 3 1.00
13.0107010 0.19682158D-01
1.9622572 0.13796524
0.44453796 0.47831935
S 1 1.00
0.12194962 1.0000000
P 1 1.00
0.8000000 1.0000000

C 0
S 5 1.00
1238.4016938 0.54568832082D-02
186.29004992 0.40638409211D-01
42.251176346 0.18025593888
11.676557932 0.46315121755
3.5930506482 0.44087173314
S 1 1.00
0.40245147363 1.0000000
S 1 1.00
0.13090182668 1.0000000
P 3 1.00
9.4680970621 0.38387871728D-01
2.0103545142 0.21117025112
0.54771004707 0.51328172114
P 1 1.00
0.15268613795 1.0000000
D 1 1.00
0.8000000 1.0000000

N 0
S 5 1.00
1712.8415853 -0.53934125305D-02
257.64812677 -0.40221581118D-01
58.458245853 -0.17931144990
16.198367905 -0.46376317823
5.0052600809 -0.44171422662
S 1 1.00
0.58731856571 1.0000000
S 1 1.00
0.18764592253 1.0000000
P 3 1.00
13.571470233 -0.40072398852D-01
2.9257372874 -0.21807045028
0.79927750754 -0.51294466049
P 1 1.00
0.21954348034 1.0000000
D 1 1.00
1.0000000 1.0000000

$end

In the output, I am getting

Maximum Overlap Method Active
MOM overlap: 66.00 / 66
Maximum Overlap Method Active
MOM overlap: 64.00 / 64
697 -748.8028172778 6.76e-06
Maximum Overlap Method Active
MOM overlap: 66.00 / 66
Maximum Overlap Method Active
MOM overlap: 64.00 / 64
698 -748.8028592003 2.43e-06
Maximum Overlap Method Active
MOM overlap: 66.00 / 66
Maximum Overlap Method Active
MOM overlap: 64.00 / 64
699 -748.8028672700 3.45e-06
Maximum Overlap Method Active
MOM overlap: 66.00 / 66
Maximum Overlap Method Active
MOM overlap: 64.00 / 64
700 -748.8028571158 4.01e-06
Maximum Overlap Method Active
MOM overlap: 66.00 / 66
Maximum Overlap Method Active
MOM overlap: 64.00 / 64
gen_scfman_exception: SCF failed to converge

Q-Chem fatal error occurred in module libgscf/gen_scfman/gen_scfman_main.C, line 218:

Error in gen_scfman

Please submit a crash report at Q-Chem Crash Reporter

In the output, SCF energy is increasing instead of decreasing at every optimization cycle. Can you please suggest to me what to do?

#2

I don’t really understand what you’re trying to do here but it feels like you’re probably jumping straight into something that is very complicated without having a good feeling for the lay of the (potential energy) landscape. Why start MOM on cycle #9? What are you trying to accomplish with that? Why use a specialized basis set rather than starting with something small? Have you optimized in the gas phase before jumping into solvent? Why excited state #4?

In general, excited-state geometry optimizations can be very tricky (not at all black-box) because you have absolutely no guarantee that you won’t see state-switching, meaning that adiabatic (Born-Oppenheimer) excited state #4 may not maintain a consistent orbital (diabatic) character as you optimize. On top of this, SF-TDDFT can suffer significant spin-contamination away from the Franck-Condon point, meaning that singlets and triplets may be mixed.

I suggest that you need to back up about 10 steps and approach this problem in stages.