summary spurious intergrated densities
any thnaks to everyone who replied. Your comments helped al lot.
Here is a summary of the answers I received:
Hi there, I have encountered the same problem a few times, and what you
have to do is to alter the grid over which the integrals are calculated. Refer
to pages 6 and 9 of the "New Methods and Features in Gaussian 92/DFT"
Notes for a complete description.
Basically one way to correct this is to compute the integrals using a
finer grid. Thiscan most easily be accomplished by using the Int=FineGrid
keyword. (gives about 7000-9000 points per atom compared with the default of
about 3000 points per atom with Int=Normalgrid).
If this fails you can define a numnber of even finer grids by following
the Grid Control Appendix in the Releas Notes on pg 9.
decker $#at#$ jcvsparc.chem.ualberta.ca
Dept. of Chemistry,
Univ. of Alberta, Canada
You need to upgrade to G94...these problems have been fixed...of get G92 Rev
John M. McKelvey email: mckelvey $#at#$ Kodak.COM
Computational Science Laboratory phone: (716) 477-3335
2nd Floor, Bldg 83, RL
Eastman Kodak Company
Rochester, NY 14650-2216
bernhard $#at#$ quant1.chemie.uni-leipzig.de
Subject: Re:DFT/spurious integrated densities
few weeks ago i struggle over the same problem.
I got the tip to add the keywords
which work in ca. 90% of all cases (using B3LYP).
The first is not fully known to me (didn't find the keyword in the
g92 manual), but i think it enhance the accuracy of the integrals
or is related to this point, the second point results in better
numerics while integration. Don't take it for good, i'm just a
If this doesn't work, then a slight alteration of the geometry helps
sometime (nearly in all remaining cases).
We have seen this problem with G92 and have made a couple of changes
which you can use with G92 that improve the situation dramatically.
Add the following Int=FINEGRID to your calculations. This may be
sufficient as it improves the integration accuracy. If not also add
SCF=NOVARACC which turns off using loose integration cutoffs on
early SCF iterations.
Both of these will increase computation time but have proven successful
enough that INT=FINEGRID is standard in G94. We have modified the cutoffs
for early iterations and seldom see this problem with G94.
Douglas J. Fox
Director of Technical Support
help $#at#$ gaussian.com