Spin of excited states from TDDFT
Clicked A Few Times
5:17:43 AM PDT - Thu, Apr 20th 2017
Dear NWChem community,

I would like to calculate the spin two (so multiplicity 5) excited states of a molecule, i.e. neither singlets nor triplets. In order to do this, I tried performing a singlet or triplet calculation, starting from a multiplicity 5 configuration. An example input file:

start TT_triplets

memory total 4000 mb

echo

GEOMETRY noautosym noautoz nocenter
C -4.36227857 -2.89231509 -4.35034344
C -4.36158698 -1.48222381 -4.35041529
C -3.51152933 -0.78490047 -3.50258695
C -2.63573885 -1.47163765 -2.62835778
C -2.63633913 -2.90501827 -2.62821488
C -3.51294598 -3.59065976 -3.50250103
H -1.75109055 -3.58866302 -1.74460125
H -0.88130838 -2.92029483 -0.87711257
C -0.88162585 -1.45831425 -0.87808105
H -1.75013735 -0.78918243 -1.74501744
H -0.00060874 -3.63108887 0.00172652
H 0.88017559 -2.92014107 0.88039669
C 0.88100433 -1.45816264 0.88066720
H -0.00013966 -0.74827117 0.00107519
H 1.74961738 -3.58840503 1.74829935
H 2.63503146 -2.90463121 2.63165492
C 2.63499478 -1.47124928 2.63105989
H 1.74971208 -0.78890240 1.74731880
H 3.51123315 -3.59019344 3.50640928
H 4.36075079 -2.89174895 4.35398313
C 4.36065204 -1.48165551 4.35330507
C 3.51097780 -0.78441715 3.50502503
C -5.03320558 -3.43555230 -5.01948809
C -3.51207269 -4.68369839 -3.50101416
C -5.03190244 -0.93828463 -5.01953200
C -3.50936731 0.30803600 -3.50098996
C -1.75664786 -4.68005159 -1.74945974
C -1.75572784 0.30192872 -1.75113041
C 1.75469251 -4.67979616 1.75389892
C 1.75567684 0.30221345 1.75287555
C 3.50985839 -4.68323080 3.50550975
C 5.03134898 -3.43491543 5.02351322
C 3.50925583 0.30852039 3.50286800
C 5.03111589 -0.93764693 5.02221792
C -4.35262750 1.48416794 4.36039981
C -4.35341783 2.89425834 4.35960886
C -3.50581678 3.59223285 3.50972962
C -2.63090006 2.90619986 2.63405558
C -2.63020343 1.47282034 2.63492559
C -3.50420389 0.78646817 3.51124438
C -1.74633378 0.78998081 1.75014787
C -0.87958723 1.45874225 0.88116052
H -0.87935502 2.92072728 0.87944728
H -1.74748106 3.58947011 1.74831347
H 0.00008527 0.74830909 0.00052136
H 0.87966359 1.45780303 -0.88096556
H 0.87871196 2.91978151 -0.88149571
H -0.00056980 3.63112176 -0.00163753
H 1.74686008 0.78813448 -1.74881314
H 2.63055221 1.47005572 -2.63446803
H 2.63044483 2.90343541 -2.63588025
H 1.74650554 3.58762451 -1.75136727
H 3.50507710 0.78280490 -3.50956777
H 4.35321419 1.47963340 -4.35971855
C 4.35316313 2.88972657 -4.36121558
C 3.50504110 3.58857051 -3.51257527
C -5.02157309 0.94052522 5.03112687
C -3.50197220 -0.30646925 3.51019523
C -5.02305027 3.43779359 5.02980700
C -3.50502982 4.68527028 3.50766878
C -1.75184000 -0.30112900 1.75679175
C -1.75321158 4.68086002 1.75262802
C 1.75288915 -0.30298134 -1.75380265
C 1.75137338 4.67900642 -1.75766699
C 3.50346832 -0.31013103 -3.50677907
C 5.02256931 0.93530500 -5.02948106
C 3.50355113 4.68160837 -3.51232836
C 5.02253072 3.43257250 -5.03223646
C -0.00061888 -5.13012795 0.00133455
C 0.86504300 -5.83921355 -0.86378101
C 0.85071377 -7.23925437 -0.84678250
C 0.00215018 -7.96216128 0.00157916
C -0.84390318 -7.24167108 0.85120670
C -0.86217672 -5.83960244 0.86687770
C 1.52549380 -7.78044084 -1.51701389
C -1.51209454 -7.78414687 1.52656571
H -0.00100708 5.13015302 -0.00281098
H -0.86479474 5.83816244 -0.86639952
H 0.86476243 5.84065660 0.86202187
H 0.84842593 7.24010203 0.84522049
H -0.00116418 7.96207625 -0.00378938
H -0.84844204 7.24082142 -0.85054544
H 1.52114068 7.78234520 1.51680087
H -1.52034097 7.78262959 -1.52264242
H 0.00453475 9.47233750 0.00385679
H -0.70448664 9.88284537 -0.73025452
H -0.27051253 9.86905300 0.99587252
H 1.00520724 9.87077833 -0.23418275
C -1.80058222 5.10656773 -1.80111928
C -2.39385178 5.81376719 -2.39898855
C -1.24762805 4.45363185 -2.49598546
C -2.49983316 4.45956670 -1.24662606
C 1.79945432 5.10741945 1.79647962
C 2.39927361 5.81349075 2.38911389
H 1.24462755 4.46113969 2.49612920
H 2.49227460 4.45330498 1.24237592
C -0.00913925 -9.47222855 -0.02013263
H -0.49950331 -9.88586838 0.87384538
H -0.55298559 -9.85392105 -0.90213704
H 1.01225269 -9.88251222 -0.06975067
C -1.79515034 -5.10879039 1.80499705
H -2.38703643 -5.81648284 2.40365127
H -1.24019811 -4.45667293 2.49903996
H -2.49567595 -4.46103530 1.25299847
C 1.80003883 -5.10522763 -1.79733936
H 2.39831725 -5.81085402 -2.39205533
H 1.24548005 -4.45670752 -2.49511192
H 2.49430791 -4.45326807 -1.24248675
END

BASIS spherical
* library cc-pvdz
END

DFT
mult 5

xc xcamb88 1.00 lyp 1.0 hfexch 1.00

cam 0.29 cam_alpha 0.0 cam_beta 1.0

direct

iterations 2000

grid nodisk
END


TDDFT
CIS

NROOTS 6

nosinglet

civecs

maxiter 500
END

task tddft energy

This however resulted in a ground state with spin <S2> = 15.0725, instead of a value around 6 for <S2> as I would like to have. The calculated excited states also have <S2> values around 15. A singlet calculation starting from the same multiplicity 5 configuration yields similar spin values, a result I cannot understand. I would appreciate if anyone has some input on that.

In general, is there a way to ask for excited states of a specific spin, e.g. 2? Thank you.

Best regards,

Antonis

Forum Regular
10:14:38 AM PDT - Thu, Apr 20th 2017
You are doing a spin-unrestricted DFT/TDDFT calculation; therefore, the keywords singlet/triplet (nosinglet/notriplet) have no meaning and are ignored by the code (hence the same result no matter which you specify). Those keywords only have meaning for a spin-restricted calculation on a closed-shell ground state.

Your DFT calculation is suffering from pretty severe spin contamination and your TDDFT inherits the same spin contamination. If you can reduce the spin contamination in the ground state, then you will likely (but no guarantee) get better excited states as far as the spin state is concerned.

Clicked A Few Times
2:01:00 AM PDT - Fri, Apr 21st 2017
Hi Sean,

thank you very much for your reply. From a quick research, the obvious way of reducing spin contamination is performing an RODFT calculation. However, it seems that there is some conflict when it comes to performing a TDDFT calculation after an RODFT, as explained in the post: http://nwchemgit.github.io/Special_AWCforum/st/id1749/error_by_running_rodft.html

Nevertheless, I tried modifying my input as follows:

start TT_triplets

memory total 4000 mb

echo

GEOMETRY noautosym noautoz nocenter
C -4.36227857 -2.89231509 -4.35034344
C -4.36158698 -1.48222381 -4.35041529
C -3.51152933 -0.78490047 -3.50258695
C -2.63573885 -1.47163765 -2.62835778
C -2.63633913 -2.90501827 -2.62821488
C -3.51294598 -3.59065976 -3.50250103
H -1.75109055 -3.58866302 -1.74460125
H -0.88130838 -2.92029483 -0.87711257
C -0.88162585 -1.45831425 -0.87808105
H -1.75013735 -0.78918243 -1.74501744
H -0.00060874 -3.63108887 0.00172652
H 0.88017559 -2.92014107 0.88039669
C 0.88100433 -1.45816264 0.88066720
H -0.00013966 -0.74827117 0.00107519
H 1.74961738 -3.58840503 1.74829935
H 2.63503146 -2.90463121 2.63165492
C 2.63499478 -1.47124928 2.63105989
H 1.74971208 -0.78890240 1.74731880
H 3.51123315 -3.59019344 3.50640928
H 4.36075079 -2.89174895 4.35398313
C 4.36065204 -1.48165551 4.35330507
C 3.51097780 -0.78441715 3.50502503
C -5.03320558 -3.43555230 -5.01948809
C -3.51207269 -4.68369839 -3.50101416
C -5.03190244 -0.93828463 -5.01953200
C -3.50936731 0.30803600 -3.50098996
C -1.75664786 -4.68005159 -1.74945974
C -1.75572784 0.30192872 -1.75113041
C 1.75469251 -4.67979616 1.75389892
C 1.75567684 0.30221345 1.75287555
C 3.50985839 -4.68323080 3.50550975
C 5.03134898 -3.43491543 5.02351322
C 3.50925583 0.30852039 3.50286800
C 5.03111589 -0.93764693 5.02221792
C -4.35262750 1.48416794 4.36039981
C -4.35341783 2.89425834 4.35960886
C -3.50581678 3.59223285 3.50972962
C -2.63090006 2.90619986 2.63405558
C -2.63020343 1.47282034 2.63492559
C -3.50420389 0.78646817 3.51124438
C -1.74633378 0.78998081 1.75014787
C -0.87958723 1.45874225 0.88116052
H -0.87935502 2.92072728 0.87944728
H -1.74748106 3.58947011 1.74831347
H 0.00008527 0.74830909 0.00052136
H 0.87966359 1.45780303 -0.88096556
H 0.87871196 2.91978151 -0.88149571
H -0.00056980 3.63112176 -0.00163753
H 1.74686008 0.78813448 -1.74881314
H 2.63055221 1.47005572 -2.63446803
H 2.63044483 2.90343541 -2.63588025
H 1.74650554 3.58762451 -1.75136727
H 3.50507710 0.78280490 -3.50956777
H 4.35321419 1.47963340 -4.35971855
C 4.35316313 2.88972657 -4.36121558
C 3.50504110 3.58857051 -3.51257527
C -5.02157309 0.94052522 5.03112687
C -3.50197220 -0.30646925 3.51019523
C -5.02305027 3.43779359 5.02980700
C -3.50502982 4.68527028 3.50766878
C -1.75184000 -0.30112900 1.75679175
C -1.75321158 4.68086002 1.75262802
C 1.75288915 -0.30298134 -1.75380265
C 1.75137338 4.67900642 -1.75766699
C 3.50346832 -0.31013103 -3.50677907
C 5.02256931 0.93530500 -5.02948106
C 3.50355113 4.68160837 -3.51232836
C 5.02253072 3.43257250 -5.03223646
C -0.00061888 -5.13012795 0.00133455
C 0.86504300 -5.83921355 -0.86378101
C 0.85071377 -7.23925437 -0.84678250
C 0.00215018 -7.96216128 0.00157916
C -0.84390318 -7.24167108 0.85120670
C -0.86217672 -5.83960244 0.86687770
C 1.52549380 -7.78044084 -1.51701389
C -1.51209454 -7.78414687 1.52656571
H -0.00100708 5.13015302 -0.00281098
H -0.86479474 5.83816244 -0.86639952
H 0.86476243 5.84065660 0.86202187
H 0.84842593 7.24010203 0.84522049
H -0.00116418 7.96207625 -0.00378938
H -0.84844204 7.24082142 -0.85054544
H 1.52114068 7.78234520 1.51680087
H -1.52034097 7.78262959 -1.52264242
H 0.00453475 9.47233750 0.00385679
H -0.70448664 9.88284537 -0.73025452
H -0.27051253 9.86905300 0.99587252
H 1.00520724 9.87077833 -0.23418275
C -1.80058222 5.10656773 -1.80111928
C -2.39385178 5.81376719 -2.39898855
C -1.24762805 4.45363185 -2.49598546
C -2.49983316 4.45956670 -1.24662606
C 1.79945432 5.10741945 1.79647962
C 2.39927361 5.81349075 2.38911389
H 1.24462755 4.46113969 2.49612920
H 2.49227460 4.45330498 1.24237592
C -0.00913925 -9.47222855 -0.02013263
H -0.49950331 -9.88586838 0.87384538
H -0.55298559 -9.85392105 -0.90213704
H 1.01225269 -9.88251222 -0.06975067
C -1.79515034 -5.10879039 1.80499705
H -2.38703643 -5.81648284 2.40365127
H -1.24019811 -4.45667293 2.49903996
H -2.49567595 -4.46103530 1.25299847
C 1.80003883 -5.10522763 -1.79733936
H 2.39831725 -5.81085402 -2.39205533
H 1.24548005 -4.45670752 -2.49511192
H 2.49430791 -4.45326807 -1.24248675
END

BASIS spherical
* library cc-pvdz
END

DFT
mult 5

xc xcamb88 1.00 lyp 1.0 hfexch 1.00

cam 0.29 cam_alpha 0.0 cam_beta 1.0

cgmin

rodft

direct

iterations 2000

grid nodisk
END


TDDFT
CIS

NROOTS 8

civecs

maxiter 500
END

task tddft energy

This gave the following two errors for a multiplicity of 5 and 3 respectively:

tddft_init: corrupted MO vectors

and

bgj_get_scf_dens: could not read mo vectors

So I was wondering if there is another way to reduce the spin contamination without using RODFT, or to make RODFT compatible with TDDFT. Thank you.

Forum Regular
5:13:00 AM PDT - Fri, Apr 21st 2017
The reason for the errors you received is the same as was explained in the other posted that you linked. It is not possible to do TDDFT from an RODFT wave function in NWChem.

Perhaps a different level of theory (xc functional/basis set) would result in less spin contamination. Otherwise DFT just might not be an appropriate method for this particular system, all methods have their limitations.


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