Hi all!
I've been having a lot of trouble while trying some basis DFT energy calculations on molecular dimers using diffuse basis sets.
This is a quite simple case: the pentacene cofacial stack (dx.doi.org/10.1021/ja061827h)
echo
title "pentacene_b3lyp_6-31+gs"
start pentacene_b3lyp_6-31+gs
geometry noautoz noautosym nocenter
C 0.000000 0.000000 1.406683
C 0.000000 1.224532 0.727541
C 0.000000 2.463824 1.406276
C 0.000000 3.672444 0.726656
C 0.000000 4.934586 1.408386
C 0.000000 6.108003 0.715689
C 0.000000 0.000000 -1.406683
C 0.000000 1.224532 -0.727541
C 0.000000 2.463824 -1.406276
C 0.000000 3.672444 -0.726656
C 0.000000 4.934586 -1.408386
C 0.000000 6.108003 -0.715689
C 0.000000 -1.224532 -0.727541
C 0.000000 -2.463824 -1.406276
C 0.000000 -3.672444 -0.726656
C 0.000000 -4.934586 -1.408386
C 0.000000 -6.108003 -0.715689
C 0.000000 -1.224532 0.727541
C 0.000000 -2.463824 1.406276
C 0.000000 -3.672444 0.726656
C 0.000000 -4.934586 1.408386
C 0.000000 -6.108003 0.715689
H 0.000000 0.000000 2.492435
H 0.000000 2.464311 2.492092
H 0.000000 4.935578 2.493484
H 0.000000 7.053599 1.245772
H 0.000000 0.000000 -2.492435
H 0.000000 2.464311 -2.492092
H 0.000000 4.935578 -2.493484
H 0.000000 7.053599 -1.245772
H 0.000000 -2.464311 -2.492092
H 0.000000 -4.935578 -2.493484
H 0.000000 -7.053599 -1.245772
H 0.000000 -2.464311 2.492092
H 0.000000 -4.935578 2.493484
H 0.000000 -7.053599 1.245772
C 3.500000 0.000000 1.406683
C 3.500000 1.224532 0.727541
C 3.500000 2.463824 1.406276
C 3.500000 3.672444 0.726656
C 3.500000 4.934586 1.408386
C 3.500000 6.108003 0.715689
C 3.500000 0.000000 -1.406683
C 3.500000 1.224532 -0.727541
C 3.500000 2.463824 -1.406276
C 3.500000 3.672444 -0.726656
C 3.500000 4.934586 -1.408386
C 3.500000 6.108003 -0.715689
C 3.500000 -1.224532 -0.727541
C 3.500000 -2.463824 -1.406276
C 3.500000 -3.672444 -0.726656
C 3.500000 -4.934586 -1.408386
C 3.500000 -6.108003 -0.715689
C 3.500000 -1.224532 0.727541
C 3.500000 -2.463824 1.406276
C 3.500000 -3.672444 0.726656
C 3.500000 -4.934586 1.408386
C 3.500000 -6.108003 0.715689
H 3.500000 0.000000 2.492435
H 3.500000 2.464311 2.492092
H 3.500000 4.935578 2.493484
H 3.500000 7.053599 1.245772
H 3.500000 0.000000 -2.492435
H 3.500000 2.464311 -2.492092
H 3.500000 4.935578 -2.493484
H 3.500000 7.053599 -1.245772
H 3.500000 -2.464311 -2.492092
H 3.500000 -4.935578 -2.493484
H 3.500000 -7.053599 -1.245772
H 3.500000 -2.464311 2.492092
H 3.500000 -4.935578 2.493484
H 3.500000 -7.053599 1.245772
end
basis
* library "6-31+g*"
end
dft
direct
convergence diis 3
maxiter 1000
grid fine
xc b3lyp
vectors input atomic output dimer.movecs
end
task dft energy
The SCF cycle starts like that:
d= 0,ls=0.0,diis 1 -1638.2924516151 -6.63D+03 2.27D+02 4.95D+03 916.0
Grid integrated density: 291.997207182703
Requested integration accuracy: 0.10E-06
d= 0,ls=0.5,diis 2 -1596.5938570357 4.17D+01 9.24D+01 4.04D+02 1147.7
Grid integrated density: 292.000933360791
Requested integration accuracy: 0.10E-06
d= 0,ls=0.5,diis 3 -533.7879528180 1.06D+03 7.82D+00 5.05D+03 1377.1
Grid integrated density: 292.002854672656
Requested integration accuracy: 0.10E-06
d= 0,ls=0.5,diis 4 -1198.9782229509 -6.65D+02 1.97D+02 2.15D+03 1606.3
Grid integrated density: 292.001966967721
...
and eventually just fails to converge:
d= 0,ls=0.5,diis 29 1352.8835222278 -1.60D+03 2.90D+00 7.18D+03 6620.0
Grid integrated density: 292.000050022126
Requested integration accuracy: 0.10E-06
d= 0,ls=0.5,diis 30 1254.6589767786 -9.82D+01 4.28D+00 5.78D+03 6825.0
Grid integrated density: 292.002613695296
Requested integration accuracy: 0.10E-06
d= 0,ls=0.5,diis 31 3773.8405074356 2.52D+03 5.69D+00 5.06D+03 7029.3
I've also tried the fragment MO method and successive projections from smaller basis (3-21g to 6-31g to 6-31g* to 6-31+g*) but nothing works...
Any input will be highly appreciated!
Best regards,
Orestis
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