Subject: Summary: When G98(W) AIM code fails

From: "Shobe, Dave" <[email-masked]>
Date: Tue, 19 Sep 2000 17:43:01 -0400

The first question, from late June 2000, was:

> I'd like to ask a more general question.  The G98 manual lists errors that
> can occur, but says nothing about ways to correct them, giving me the
> impression that if the AIM code fails for any reason, you're out of luck.
> Is there anything one can do when the AIM calculations fail?
>
> --David Shobe

(This was, in return, prompted by a question by Alejandro Montoya about a
specific error message).

The consensus answer (thanks to Frederick P. Arnold, Jr., Stefan Fau, and
Jim Kress) is that one is indeed out of luck as far as Gaussian is
concerned, but that the AIMPAC code written by Bader et al. is still
available at http://www.chemistry.mcmaster.ca/aimpac/.  It's much slower
than Gaussian, but doesn't fail as often.  I did get an answer from Gaussian
Inc., which I have included at the end of this message. (But basically they
don't have any suggestions).

But the description of AIMPAC on the abovementioned web site led me to the
following questions:

> A few more questions about options when G98W fails:
>
> #1.  The AIMPAC download webpage
> http://www.chemistry.mcmaster.ca/aimpac/
> describes the programs as being "vectorized".
> Will these run on my computer, which is not only a single-processor
machine,
> but
> is Windows rather than Unix or Linux?
> 
> #2.  Is it possible to get bond orders, or has Cioslowski et al only made
> these available thru Gaussian?

[There was a #3, but it was more of a rant than a question and I will not
include it here.]

Again there is a consensus (thanks this time to Joel Foreman, Cherif F.
Matta, and Fred Arnold) that for Windows, the program to use is AIM2000,
which is available for free at http://gauss.fh-bielefeld.de/aim2000/.  I'm
still "playing with" AIM2000, but it looks like this is indeed what I want.
(Although I was somewhat disappointed that I can't display the interatomic
surfaces, and more disapointed by the inability to cut and paste to other
applications).

Fred Arnold also mentioned Morphy (web site:
http://www.ch.umist.ac.uk/morphy/), which has a free demo version, although
one is restricted to 10 atoms and 200 primitive Gaussian functions.

--David Shobe
Süd-Chemie Inc.
phone (502) 634-7409
fax     (502) 634-7724
email  [email-masked]

Any opinions herein are not necessarily representative of Süd-Chemie.

+++++++++++++++++++++++++++++++++++++++++++++
Appendix: Gaussian's reply to my first question:

   The fixes are not trivial if they exist.  SVDSol has no options you
can tweak from the input and in your case I can't make much of a 
suggestion since the problem seems to run on other machines.

   The parameters you can control are given in the source at the top of
g98/l609.F and you can relax some of the numerical cutoffs with the
tradeoff that you have less precision in the results.