Hello everyone,

I have a question regarding the optimization of the platinum complex. I used the CAM-B3LYP/def2-SVP level of theory. However, the SCF did not converge using 2000 cycles. Also I used DIIS_GDM algorithm which was not helpful. Do you have any suggestions for optimizing such complex.

Any suggestions will be appreciated.

Thanks!

Can you provide an input of this job?

I have just sent to you by email.

I have not received an email, just post the input here on this forum. You can use Markdown to assist in the formatting if you want.

$molecule

0 1

N -2.0603938 -0.0197441 0.1340280

N 1.8279481 0.0306489 -0.2826619

N -0.0811053 2.0294311 -0.0344797

N -0.0468057 -1.9835564 -0.1052060

C -2.8407651 1.0622832 0.0454246

C -2.8189398 -1.1190911 0.0164968

C 2.5379768 1.1197274 -0.6140410

C 2.5600799 -1.0373083 -0.6339654

C -2.4199150 2.4618800 0.1193542

C -2.3739716 -2.4989719 0.0790898

C 2.3437158 2.3679113 -0.2375938

C 2.3955680 -2.2881585 -0.2764946

C -1.1364634 2.8187354 0.1974980

C -1.0846565 -2.8054996 0.1309200

C 1.0268950 2.7782748 0.1306595

C 1.0775357 -2.7128236 0.0499090

C -4.1158463 0.6237627 -0.0576959

C -4.1014463 -0.7190285 -0.0648235

C 3.4235135 0.7246368 -1.5543397

C 3.4390658 -0.6173349 -1.5568888

C -3.4676453 3.5158855 0.0639255

C -3.3945655 -3.5842712 0.0603383

C 3.5120143 3.3138606 -0.0715702

C 3.5926482 -3.2125517 -0.0954209

C -0.6631415 4.0576043 0.5444062

C -0.5838709 -4.0145809 0.5438368

C 0.6715051 4.0327983 0.5088867

C 0.7532193 -3.9434656 0.5053766

C -3.8457818 4.0525515 -1.1917176

C -4.0559078 -4.0218451 1.2285214

C -4.1345490 3.9498229 1.2221459

C -3.7618158 -4.1423040 -1.1874604

C 4.1694996 3.3287658 1.1974855

C 3.9783298 -4.1887499 -1.0257225

C 3.8761229 4.2906093 -1.0073333

C 4.2488850 -3.2232711 1.1791610

C -4.8338518 5.0424005 -1.2642075

C -4.9693274 -5.0789223 1.1580708

C -5.0740034 4.9795385 1.1450406

C -4.7273816 -5.1528596 -1.2519985

C 5.1822259 4.2599274 1.4793585

C 5.0251572 -5.0796719 -0.7475151

C 4.9080547 5.1976982 -0.7309984

C 5.2783753 -4.1401235 1.4628849

C -5.4263301 5.5232292 -0.0933882

C -5.3077362 -5.6396588 -0.0776964

C 5.5625190 5.1819354 0.5048449

C 5.6784615 -5.0535015 0.4881270

C -5.3007320 1.2954363 -0.1474705

C -5.2651001 -1.4391569 -0.1122675

C 4.0624193 1.4509877 -2.5363961

C 4.1050570 -1.3364443 -2.5163137

C -1.2934694 5.1882746 0.9874633

C -1.1867705 -5.1487380 1.0600829

C 1.4110318 5.1552048 0.8182151

C 1.5285977 -5.0008962 0.9364396

H -3.4022658 3.6872905 -2.1127724

H -3.7872173 -3.6032328 2.1871764

H -3.8535843 3.5421967 2.1818575

H -3.3252350 -3.7719593 -2.1092614

H 3.8672081 2.6567439 1.9954924

H 3.4539750 -4.2749485 -1.9595045

H 3.3503144 4.3630007 -1.9418245

H 3.9319889 -2.5660749 1.9835505

H -5.1372266 5.4438731 -2.2245141

H -5.4033106 -5.4706021 2.0674789

H -5.5199692 5.3592200 2.0525323

H -5.0189614 -5.5664715 -2.2105787

H 5.6657813 4.2778431 2.4540695

H 5.3156495 -5.8088427 -1.4905047

H 5.1883155 5.9280145 -1.4760063

H 5.7593105 -4.1572768 2.4401333

H -6.1654504 6.3123353 -0.1430984

H -6.0244259 -6.4496321 -0.1240573

H 6.3509351 5.8973859 0.7120606

H 6.4782387 -5.7576584 0.6958830

Pt -0.1232491 0.0244828 -0.0736815

C -0.6310828 6.3870126 0.8082304

C 0.7513660 6.3822045 0.6668215

C -6.4536968 0.5999059 0.1183492

C -6.4290114 -0.7946085 0.2154290

C -0.4435279 -6.2555197 1.3874783

C 0.9289020 -6.1663939 1.3410979

C 5.0779813 0.7720919 -3.1978683

C 5.1118415 -0.6457607 -3.1592183

H -5.3793224 2.3188747 -0.3076014

H -5.3118526 -2.4586203 -0.2880808

H 3.8061145 2.4830533 -2.7188026

H 3.8871697 -2.3773914 -2.6965345

H -2.2596698 5.1612785 1.3433829

H -2.1818568 -5.2326597 1.2512324

H 2.4351936 5.0638902 1.0361237

H 2.5632913 -4.9832049 0.9988388

H -1.1821182 7.3048569 0.8307504

H 1.2706771 7.3211169 0.5379287

H -7.3257173 1.1958580 0.2303482

H -7.2690483 -1.4149623 0.4858337

H -0.9262928 -7.1625161 1.7003179

H 1.5449988 -6.9778155 1.6414494

H 5.7990613 1.3563965 -3.7308796

H 5.8653512 -1.2466412 -3.6165733

$end

$rem

JOBTYPE = OPT

EXCHANGE = cam-b3lyp

BASIS = def2-SVP

GEOM_OPT_MAX_CYCLES = 2000

GUI = 2

MAX_SCF_CYCLES = 2000

MEM_STATIC = 5000

MEM_TOTAL = 250000

SYM_IGNORE = TRUE

$end

I have just copied my input file. I hope it is fine.

So their are several factors that are leading to your trouble with optimization of this molecule. The first problem is that your starting geometry is not the best starting position you can construct for this molecule. The symmetry of the molecule is roughly D4h but the structure that you start at is C1 since the benzene rings and indole fragments are not symmetric with each other. Therefore I suspect most of the optimization cycles are spent trying to reach D4h.

To fix this problem there are two approaches, first being to reduce your basis to something simple like 6-31g. Once you have that optimized structure use that as your starting geometry for def2-SVP. Second approach is to improve the construction of your starting geometry. The molecule you include looks very similar to the tetrabenzoporphyrin fragment that is available in IQmol. So use that as the starting point since it is already an optimized piece and D2h. Then build up the rest of your desired molecule (add the benzene’s and Pt). That structure will be closer than the one your provided.

Sorry you will have to use dual basis, since you have the Pt. Or you can remove the Pt and run optimization on the organic portions with 6-31g then when that job completes add the Pt back into the structure and use def2-SVP.

Thanks alot! I will try the options you mentioned and let you know in case I have problem.

Just a quick addendum (I think all of Peter’s suggestions are good ones): SCF convergence failure is almost always a result of a poor guess. Changing SCF_ALGORITHM helps occasionally but you are generally better off looking for a better guess, generally with BASIS2, which converges first in a small basis and then projects that solution into the target basis as an initial guess for the latter… If the metal causes problems in that capacity, you can define a custom basis (BASIS=GEN and $basis section), then use SCF_GUESS=AUTOSAD to get the superposition of atomic densities guess in the custom basis. I would try these suggestions in that order, i.e., BASIS2 first.

Did your SCF fail to converge in the starting geometry or after some geometry optimization steps?

The SCF did not converged after 16 steps.

Please try SCF_GUESS_ALWAYS = true.