Simple dimer DFT calculation with diffuse basis set


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Please try this modified input that will converge in 18 iterations

echo
title "pentacene_b3lyp_6-31+gs"
start  pentacene_b3lyp_6-31+gs

geometry noautoz 
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 spherical
 * library "6-31+g*"
end

dft
 direct
# convergence diis 3
 maxiter 1000
 grid fine
 xc b3lyp
 vectors input atomic output dimer.movecs
 smear
 convergence ncydp 0 damp 45 dampon 1d99 dampoff 1d-4
end
set quickguess t
task dft energy