So I am new to NWchem and am trying to use it to do CDFT combined with the electronic coupling module to model charge transfer. The end goal is to model charge transfer between a C54H18 cluster and redox active molecules. To get started I thought it first would be good to do something like charge transfer between two anthracence molecules. So I have been trying to do constrained DFT to get the movecs of an electron constrained to either the left or right anthracence facing each other in a planar fashion. I started with 4Angstrom separation. I have been having great difficulty getting the CDFT to converge seemingly trying all the tricks I found on the forum.
So in summary I want to calculate the movecs for AminusA and AAminus where A is anthracene. The following is a example input I tried for computing the AminusA. Note: the left coordinates are relaxed in the charged state while the right coordinates are relaxed in the nuetral state. In this attempt I try to use the fragments method to give the CDFT a good starting guess, but it does not work very well. I also tried the default guess for the movecs for the CDFT part and it will converge for the left configuration using the Lowdin partitioning but not Becke. The right configuration does not converge with the default guess for the movecs.
I am using 6.8.1.
start anthracence_charge_transfer
scratch_dir ./tmpdir
geometry left_a nocenter noautoz noautosym
C 15.7264 13.758 -2
C 16.3998 12.5057 -2
C 15.7033 11.295 -2
C 14.2967 11.295 -2
C 13.6002 12.5057 -2
C 14.2736 13.758 -2
H 17.4892 12.5056 -2
H 16.2497 10.3536 -2
H 13.7503 10.3536 -2
H 12.5108 12.5056 -2
C 13.596 15 -2
C 14.2736 16.242 -2
C 15.7264 16.242 -2
C 16.404 15 -2
H 12.5061 15 -2
H 17.4939 15 -2
C 13.6002 17.4943 -2
C 14.2967 18.705 -2
C 15.7033 18.705 -2
C 16.3998 17.4943 -2
H 12.5108 17.4944 -2
H 13.7503 19.6464 -2
H 16.2497 19.6464 -2
H 17.4892 17.4944 -2
End
geometry right_a nocenter noautoz noautosym
C 15.7229 13.7752 2
C 16.4083 12.5185 2
C 15.7138 11.3357 2
C 14.2862 11.3357 2
C 13.5917 12.5185 2
C 14.2771 13.7752 2
H 17.4953 12.5195 2
H 16.2479 10.3899 2
H 13.7521 10.3899 2
H 12.5047 12.5195 2
C 13.5951 15 2
C 14.2771 16.2248 2
C 15.7229 16.2248 2
C 16.4049 15 2
H 12.5072 15 2
H 17.4928 15 2
C 13.5917 17.4815 2
C 14.2862 18.6643 2
C 15.7138 18.6643 2
C 16.4083 17.4815 2
H 12.5047 17.4805 2
H 13.7521 19.6101 2
H 16.2479 19.6101 2
H 17.4953 17.4805 2
End
geometry combined nocenter noautoz noautosym
C 15.7264 13.758 -2
C 16.3998 12.5057 -2
C 15.7033 11.295 -2
C 14.2967 11.295 -2
C 13.6002 12.5057 -2
C 14.2736 13.758 -2
H 17.4892 12.5056 -2
H 16.2497 10.3536 -2
H 13.7503 10.3536 -2
H 12.5108 12.5056 -2
C 13.596 15 -2
C 14.2736 16.242 -2
C 15.7264 16.242 -2
C 16.404 15 -2
H 12.5061 15 -2
H 17.4939 15 -2
C 13.6002 17.4943 -2
C 14.2967 18.705 -2
C 15.7033 18.705 -2
C 16.3998 17.4943 -2
H 12.5108 17.4944 -2
H 13.7503 19.6464 -2
H 16.2497 19.6464 -2
H 17.4892 17.4944 -2
C 15.7229 13.7752 2
C 16.4083 12.5185 2
C 15.7138 11.3357 2
C 14.2862 11.3357 2
C 13.5917 12.5185 2
C 14.2771 13.7752 2
H 17.4953 12.5195 2
H 16.2479 10.3899 2
H 13.7521 10.3899 2
H 12.5047 12.5195 2
C 13.5951 15 2
C 14.2771 16.2248 2
C 15.7229 16.2248 2
C 16.4049 15 2
H 12.5072 15 2
H 17.4928 15 2
C 13.5917 17.4815 2
C 14.2862 18.6643 2
C 15.7138 18.6643 2
C 16.4083 17.4815 2
H 12.5047 17.4805 2
H 13.7521 19.6101 2
H 16.2479 19.6101 2
H 17.4953 17.4805 2
End
BASIS
END
charge -1
set geometry left_a
dft
xc b3lyp
mult 2
ODFT
iterations 1000
convergence nolevelshifting
convergence energy 1d-6
convergence damp 50
convergence ncydp 100
vectors output left_avecs.movecs
end
task dft
charge 0
set geometry right_a
dft
xc b3lyp
mult 1
ODFT
iterations 1000
convergence nolevelshifting
convergence energy 1d-6
convergence damp 50
convergence ncydp 100
vectors output right_avecs.movecs
end
task dft
charge -1
set geometry combined
dft
xc b3lyp
convergence nolevelshifting
mult 2
ODFT
vectors input fragment left_avecs.movecs right_avecs.movecs output left_cdft.movecs
iterations 1000
grid fine
convergence damp 70
convergence ncydp 100
convergence energy 1d-6
cdft 1 24 charge -1
end
set dft:cdft_maxiter 20000
task dft
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