Subject: summary spurious intergrated densities

From: Uli Salzner <[email-masked]>
Date: Wed, 29 Nov 1995 12:13:45 -0330 (NST)

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" Release
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.

                                Stephen Decker
                                [email-masked]
                                Dept. of Chemistry,
                                Univ. of Alberta, Canada

You need to upgrade to G94...these problems have been fixed...of get G92 Rev
Level F.

Regards..

John

--

John M. McKelvey                        email: [email-masked]
Computational Science Laboratory        phone: (716) 477-3335
2nd Floor, Bldg 83, RL
Eastman Kodak Company
Rochester, NY 14650-2216

     [email-masked]
Subject: Re:DFT/spurious integrated densities

Hi,

few weeks ago i struggle over the same problem.
I got the tip to add the keywords

SCF=NoVarACC INT=FineGrid

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
starter...
If this doesn't work, then a slight alteration of the geometry helps
sometime (nearly in all remaining cases).

Bernhard Eck

  Dr. Salzner,

   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
  [email-masked]