Hi,

I am trying to calculate the vibrational frequencies of the ground state for 2-methylAnthracene and I couldn’t get rid of the imaginary frequency. I tried some commonly used trics such as tightening the convergence criteria, using stability analysis and tweaking the geometry a bit along with the complex normal mode but that didn’t help.

Here is my input file:

$molecule

0 1

C 0.8681005 0.5236808 0.0000397

C -0.2907264 1.3131490 0.0000945

H -0.1941351 2.4002659 0.0001735

C -1.5730942 0.7421661 0.0000498

C 2.1824337 1.0948542 0.0000893

H 2.2716681 2.1828136 0.0002187

C 3.3138750 0.3145431 0.0000260

C 3.1662560 -1.1133953 -0.0000489

H 4.0640240 -1.7336604 -0.0000539

C 1.9303747 -1.7046712 -0.0000956

H 1.8388077 -2.7914802 -0.0001248

C 0.7355414 -0.9147021 -0.0000675

C -0.5435393 -1.4871912 -0.0000997

H -0.6400596 -2.5742783 -0.0001685

C -1.7037944 -0.6975034 -0.0000465

C -2.7635610 1.5378912 0.0001039

H -2.6653469 2.6241624 0.0001757

C -4.0046880 0.9512522 0.0000726

H -4.9020261 1.5702941 0.0001186

C -4.1334131 -0.4708129 -0.0000197

H -5.1272312 -0.9187378 -0.0000419

C -3.0164716 -1.2687908 -0.0000772

H -3.1126252 -2.3552333 -0.0001475

C 4.6984263 0.9113910 -0.0001720

H 4.6419423 2.0353429 0.6390515

H 5.0499419 1.1293476 -1.1342601

H 5.4824402 0.175325 0.6039344

$end

$rem

BASIS = aug-cc-pVDZ

GEOM_OPT_MAX_STEP_SIZE = 999

GEOM_OPT_TOL_DISPLACEMENT = 120

GEOM_OPT_TOL_ENERGY = 1

GEOM_OPT_TOL_GRADIENT = 10

GUI = 2

INTERNAL_STABILITY = 1

JOB_TYPE = Optimization

MEM_STATIC = 2000

MEM_TOTAL = 80000

METHOD = B3LYP

MOLDEN_FORMAT = 1

PURECART = 2222

SCF_CONVERGENCE = 8

SYM_IGNORE = 1

THRESH = 14

$end

@@@

$comment

Freq

$end

$molecule

read

$end

$rem

BASIS = cc-pVDZ

GUI = 2

JOB_TYPE = Frequency

MEM_STATIC = 2000

MEM_TOTAL = 80000

METHOD = B3LYP

MOLDEN_FORMAT = 1

SCF_CONVERGENCE = 8

SYM_IGNORE = 1

$end

Any suggestion is very helpful. Thank you