Please provide the input file

chk=opt.chk

%mem=1500MW

%nprocs=6

#uB3LYP gen 5d SCF=(MaxCycle=3000) pseudo=cards Test opt(modredundant,loose) freq pop=full nosymm

No Title

1 5

C 42.177000000 36.551000000 28.767000000

H 42.117000000 35.501000000 28.483000000

H 43.079000000 36.655000000 29.381000000

N 40.994000000 36.877000000 29.571000000

H 40.103000000 36.446000000 29.310000000

C 40.962000000 37.837000000 30.526000000

N 42.023000000 38.650000000 30.692000000

H 42.075000000 39.363000000 31.442000000

H 42.797000000 38.608000000 30.050000000

N 39.876000000 37.989000000 31.287000000

H 39.774000000 38.882000000 31.793000000

H 39.140000000 37.276000000 31.334000000

N 36.420000000 42.574000000 34.937000000

H 35.490000000 42.589000000 34.510000000

C 36.879000000 41.694000000 35.915000000

C 37.389000000 43.497000000 34.698000000

H 37.336000000 44.277000000 33.959000000

N 38.448000000 43.259000000 35.489000000

C 38.138000000 42.132000000 36.252000000

H 38.825000000 41.742000000 36.979000000

N 40.940000000 43.523000000 39.639000000

H 40.645000000 43.589000000 40.603000000

C 41.916000000 42.657000000 39.150000000

C 40.412000000 44.212000000 38.587000000

H 39.635000000 44.949000000 38.679000000

N 41.003000000 43.835000000 37.445000000

C 41.946000000 42.862000000 37.791000000

H 42.566000000 42.397000000 37.045000000

C 45.414000000 44.285000000 37.589000000

H 45.225000000 43.318000000 38.060000000

H 44.670000000 44.997000000 37.947000000

S 45.075000000 44.099000000 35.723000000

N 38.923000000 48.277000000 36.825000000

H 39.096000000 49.289000000 37.026000000

C 37.822000000 47.491000000 37.148000000

C 39.880000000 47.463000000 36.300000000

H 40.843000000 47.798000000 35.958000000

N 39.442000000 46.202000000 36.276000000

C 38.157000000 46.205000000 36.804000000

H 37.594000000 45.291000000 36.866000000

N 44.546000000 45.354000000 32.094000000

H 44.519000000 45.206000000 33.096000000

C 45.312000000 44.649000000 31.174000000

C 43.717000000 46.192000000 31.391000000

H 43.015000000 46.853000000 31.866000000

N 43.916000000 46.058000000 30.080000000

C 44.916000000 45.099000000 29.935000000

H 45.283000000 44.822000000 28.961000000

C 47.148000000 40.478000000 35.654000000

C 46.674000000 41.752000000 36.011000000

H 47.137000000 42.309000000 36.813000000

C 45.607000000 42.358000000 35.346000000

C 44.951000000 41.658000000 34.313000000

O 43.923000000 42.269000000 33.628000000

H 43.327000000 41.629000000 33.076000000

C 46.464000000 39.781000000 34.645000000

H 46.755000000 38.772000000 34.365000000

C 45.375000000 40.359000000 33.989000000

H 44.836000000 39.812000000 33.222000000

N 41.175000000 42.699000000 34.497000000

H 40.848000000 41.906000000 35.050000000

C 40.684000000 42.595000000 33.096000000

H 39.603000000 42.738000000 33.113000000

C 41.308000000 43.658000000 32.207000000

H 42.398000000 43.653000000 32.215000000

H 40.930000000 43.569000000 31.186000000

S 40.786000000 45.420000000 32.751000000

C 40.941000000 41.197000000 32.527000000

O 42.184000000 40.794000000 32.421000000

O 39.925000000 40.507000000 32.222000000

H 42.197000000 42.767000000 34.530000000

Fe 40.264000000 44.456000000 35.440000000

O 41.670000000 45.553000000 34.249000000

O 39.220000000 45.098000000 33.328000000

H 42.216020211 37.205751542 27.908991934

H 48.011298673 40.048518895 36.140478551

H 46.422367759 44.607021048 37.803235635

H 42.522352915 41.968438688 39.719753861

H 46.062771983 43.902409750 31.386942310

H 36.891154469 47.825064482 37.581967187

H 36.354102891 40.843338266 36.323971440

O 44.320566568 46.983705777 35.491440199

O 43.459688136 47.806450304 35.455983505

X 1 F

X 15 F

X 49 F

X 35 F

X 23 F

X 43 F

X 29 F

Fe 0

Lanl2dz

****

C H O N S 0

6-31G*

****

Fe 0

Lanl2dz

This problem arises from difficulty in SCF convergence. If you have used #P, then you will find nearly 200 SCF cycles have passed while convergence criteria have not been met.

You used too many redundant keywords, "5d SCF=(MaxCycle=3000) pseudo=cards Test" should be removed, and "gen" should be replaced with "genecp".

While searching solutions on the internet I came across with the keyword QC for opt. Right now the calculation works fine but it is too slow.

Sure, the quadratically convergent method is more expensive than DIIS, however, this is the best way to reach convergence. Best regards.

Thank you for the answer. Would it be a problem if I use the geometry that is optimized with QC keyword (10 15 cycle) and then run without QC so that the calculation can be achieved faster ?

Nop, no problem, you can try that strategy. If you get SCF problems with the new geometry  then you must use QC again.

Thank you again for your time and effort to answer my questions

I think Tian Lu is right,

Yes Tian Lu is correct thus the route may include #uB3LYP GENECP SCF=XQC the part SCF=XQC is included to overcome any convergence problem.