Subject: Summary: Problems with G92-DFT

From: [email-masked] (John Lohrenz)
Date: Fri, 29 Apr 94 13:20:58 MDT

Some days ago I posted a query to the net about problems with
G92-DFT. I was asked to summerize the answers what I want to do with
this mail. The most important information was that GAUSSIAN is
working on this problem and that a new release will be presented
(hopefully soon). A good hint was to combine a finer grid with
SCF=NoVarAcc (N.v.Eikema Hommes) which worked at least in my
"problem cases". Special thanks for this detailed answer. Following
are the explicit answers (I had to translate the one by Nico, hopefully
you get the message).

Thanks again for all answers, 

John

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The original question was:

>Dear netters,
>
>not too long ago I started to carry out DFT calculations using
>G92. Quite frequently my calculations run into the following
>problem:
>    Warning! Spurious integrated density
>
>I encountered this error in many different calculations using the
>BLYP or the SVWN functionals with the 3-21G(d) or the 6-31G(d) basis
>set. Both singlet and triplet calculations gave similar mistakes. Some=
>times it helped to use guess=always, but I think there should be better
>and faster possibilities...
>Can someone out there tell me what this means and even more important
>how can I prevent my calculations to run into this error.
>

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Nico van Eikema Hommes writes (in short):

Possible solutions are:
1. simply comment the call in link1e. The calculation continues and one 
   realizes that:
2. the problem disappears completely or becomes remarkably less grave when
   the convergence criterium is fulfilled. Consequently the reason is the
   initial guess (projected INDO or Ae), which is quite bad.
    (Let me state at this point, that from time to time my calculations got
     through only when I used the INDO guess, they failed with a guess 
     read from the read-write file. How can we understand this?)
3. With INT=FINEGRID and SCF=NOVARACC (SCF=(NOVARACC,TIGHT) for single
   point calculations) the problem arises only with extended basis sets
   like 6-311+G* etc. Therefore these keyword have to be used here in 
   Erlangen. The default grid is far too rough!
4. Interestingly convergence problems seem to be less grave with this 
   option. However it is better to carry out a HF-single-point calculation 
   than the SCF=QC (suggested by GAUSSIAN inc.) if convergence is still a
   problem (unless you have plenty of computer time).
Finally one has to realize that frequency jobs are very slow.

However G92/DFT is a very nice extension and usage is easier than ADF
or DGauss.

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the original message follows: