transition state searchin

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Dear all,

I'm not that new to comp.chem. but the innings of nwchem sometimes dazzle me...

I'm searching for a transition state of some "well-behaved" but somewhat large systems. i managed to find them out at semi-empirical level rather easily, and also at a b3lyp/6-31+g*, which is what i actually need, but using a software i can only use for testing and not for production (money issues involved).

In NWChem I simply cannot find it.
I've tried:
- starting from the semi-empirical TS and simply using "task dft saddle";
- starting from the semi-empirical TS and setting the two relevant bonds equal, optimizing, removing the restrains, and finding the saddle point, as hereafter:
geometry adjust
 zcoord
  bond 33 20 r1 
  bond 19 14 r1
 end
end

task dft optimize

geometry adjust
 zcoord
  bond 33 20 ra 
  bond 19 14 rb
 end
end

task dft saddle


- both the previous approaches, starting with 3-21g and then using 6-31+g*;
- both the four previous approaches, starting with "task scf" and moving on to "task dft".

I've tried from 512 to 16384 cores, from 1h to 12h, and it never converges; the best result i got so far is this one, using 409 cores in 3 hours; basically Energy will continue going up and down for hours:
@ Step       Energy      Delta E   Gmax     Grms     Xrms     Xmax   Walltime
@ ---- ---------------- -------- -------- -------- -------- -------- --------
@    0   -1370.07402942  0.0D+00  0.04007  0.00584  0.00000  0.00000   3227.0
@    1   -1390.09356448 -2.0D+01  0.19141  0.02730  0.18810  0.70698   3621.9
@    2   -1405.16078729 -1.5D+01  4.41203  0.35142  0.66656  2.33209   3926.9
@    3   -1395.06021814  1.0D+01  0.46875  0.04920  0.01224  0.03950   4341.4
@    4   -1391.84280854  3.2D+00  0.20524  0.03234  0.28838  0.96386   4599.3
@    5   -1390.34902276  1.5D+00  0.41416  0.03152  0.27279  0.80297   4945.5
@    6   -1391.37084310 -1.0D+00  0.15604  0.02646  0.06094  0.21887   5226.3
@    7   -1387.37461692  4.0D+00  6.23294  0.75855  0.48296  1.64532   5639.6
@    8   -1409.51832805 -2.2D+01  3.35162  0.21275  0.31449  1.33895   6082.9
@    9   -1411.46980249 -2.0D+00  0.80072  0.12469  0.35833  1.04045   6369.8
@   10   -1418.94320046 -7.5D+00 11.40609  1.65839  0.03230  0.11637   6814.3
@   11   -1409.56152186  9.4D+00  1.02348  0.11676  0.00497  0.01507   7484.3
@   12   -1405.06149710  4.5D+00  3.58403  0.21298  0.36337  0.93229   7737.0
@   13   -1400.18805699  4.9D+00  0.27405  0.03565  0.00261  0.00838   7957.2
@   14   -1400.90597963 -7.2D-01  0.35446  0.04281  0.00019  0.00068   8168.2
@   15   -1395.67115410  5.2D+00  0.26135  0.03761  0.00330  0.01143   8385.1
@   16   -1393.84956516  1.8D+00  0.11285  0.02409  0.12495  0.39939   8606.4
@   17   -1395.58405244 -1.7D+00  0.52558  0.07931  0.25719  0.86397   9037.0
@   18   -1399.34965134 -3.8D+00  0.61906  0.04839  0.26580  1.02865   9358.5
@   19   -1405.85472854 -6.5D+00  6.87758  0.56548  0.85591  2.12683   9591.4
@   20   -1398.84413270  7.0D+00  3.93401  0.30363  0.54737  1.58926  10032.6
@   21   -1420.13246889 -2.1D+01  6.50849  0.38982  0.33090  0.99010  10596.9


Are there any approaches I can use to achieve convergence, or is it really a question of time ?

FYI, this same system using the other software converged in 2 weeks with 6 cores on my PC.

I'm attaching in the end the nw file for this example.

Thanks for your time,
E.

memory total 6 gb
start nvp-ts-122
geometry
C 0.00000000 0.00000000 0.00000000
C 1.38819303 0.00000000 0.00000000
C 2.05714020 1.23387879 0.00000000
N 1.41173603 2.40902533 -0.02951515
C 0.05397831 2.40887368 -0.04991691
C -0.69660506 1.21596325 -0.02259409
N -0.60323441 3.65984770 -0.00913331
C -1.47451841 3.90201758 -1.11455132
C -2.68660457 3.16794381 -1.26002907
N -1.12002529 4.89683531 -1.95002306
C -1.96124792 5.25549522 -2.93281358
C -3.20246561 4.64010765 -3.10697993
C -3.58304261 3.59631633 -2.26036756
C -2.15795576 1.15269493 0.09941145
N -3.02397940 2.10488246 -0.40408836
C 0.21218588 4.80508872 0.40414713
C -0.51338105 5.88103623 1.19121266
C 0.43723393 4.94617997 1.89859875
O -2.68230243 0.20385591 0.67467194
C -4.98832124 3.07019628 -2.42541451
H -0.56167060 -0.94126392 0.02806185
H 1.94918329 -0.93011407 0.00896086
H 3.15435684 1.29970786 0.01494971
H -1.61292766 6.06646326 -3.58422168
H -3.86562352 4.98116227 -3.89900363
H 1.00762783 5.07575064 -0.30545644
H -1.58227696 5.78942131 1.36873272
H -0.24547617 6.92096525 1.03140507
H 0.04076995 4.19383901 2.57627965
H 1.39919545 5.30358956 2.25409076
H -5.39131797 3.34567833 -3.42840807
H -5.63997354 3.59240013 -1.67737532
N -5.07147453 1.61478438 -2.17492323
C -6.46994862 1.12381517 -2.17675949
C -6.47563023 -0.35164827 -1.73944610
C -6.13805043 -0.48414174 -0.24929295
C -5.97154116 -1.95718371 0.13736138
C -5.67394366 -2.14025197 1.61035072
C -5.64185034 -3.75396642 1.92039460
N -4.28691725 -1.65088930 1.97436488
O -6.70564138 -4.31336291 1.78348652
O -4.49786285 -4.10281657 2.24359786
H -6.43407699 -1.67904680 2.26165178
H -4.49825692 1.09502708 -2.84013786
H -4.02874978 1.82429252 -0.43150598
H -6.95427999 1.23076646 -3.17088788
H -7.06508397 1.73346399 -1.46199524
H -5.75644924 -0.93415591 -2.34676405
H -7.46985563 -0.79372981 -1.94438982
H -5.20974079 0.08113504 -0.03193829
H -6.93232886 -0.01578371 0.36115442
H -5.19083994 -2.43821664 -0.48593786
H -6.90417272 -2.52480515 -0.09717697
H -4.28929187 -1.14190667 2.85740286
H -3.68704264 -2.53512002 2.09672373
H -3.88297705 -1.04222999 1.24933958
end

driver
loose
maxiter 250
end

basis
* library 6-31+g*
end

scf
maxiter 250
end

dft
xc b3lyp
iterations 250
end

geometry adjust
zcoord
bond 33 20 r1
bond 19 14 r1
end
end

task scf optimize

task dft optimize

geometry adjust
zcoord
bond 33 20 ra
bond 19 14 rb
end
end


basis
* library 6-31+g*
end

task dft saddle


  • Bylaska Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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The results you're showing look like something is really broken. Fluctuations in total energy of +20 hartrees (>1/2 keV) is not normal. I'll try to run your input and let you know what happens

  • Bylaska Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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I'm not sure I understand your input. Right now you're during your constrained geometry optimization your trying to make the distance of an N-C bond the same as a C-O bond and these bonds are separated by 4 bonds.


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