Subject: Symmetry bug

From: [email-masked] (Alan Shusterman)
Date: 08 May 97 10:25:45 PDT

I run into the following bug every few weeks:

I build a molecule with a certain symmetry (Cs in this case) and optimize its
structure with symmetry ON.  Then I try to reoptimize its structure with a
larger basis set while still using symmetry, but Spartan stops with the
following error message:

SPARTAN AB INITIO PROGRAM

Molecule (C1) and archive (CS) have differenty symmetry. Calculation
terminating.

Can anyone tell me at what point the molecule adopted C1 symmetry? (The input
file and the molecule on the scree both still have CS symmetry).  Does anyone
have any advice on how to proceed? (I really want to do the larger basis set
with symmetry, so I need to convince Spartan that the molecule does have CS
symmetry.)

Note: transferring the coordinates in the archive (CS) to the input file
doesn't help (Spartan already did this automatically when I set up the
calculation for the larger basis set). Spartan still thinks the molecule is C1
and the archive is CS.

Alan

Alan Shusterman
Department of Chemistry
Reed College
Portland, OR

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From: Dale Andrew Braden <[email-masked]>
Date: Thu, 8 May 1997 17:37:50 -0700 (PDT)

Dear Alan,

I have had all kinds of problems with Spartan in controlling molecular
symmetry, and I have rarely been able to work around them.  Spartan seems
to use rather loose cutoffs in determining molecular symmetry.  The
Builder would tell me that the molecule had Cs symmetry, but when I
transferred the coordinates to Gaussian 94, it was C1.  I looked at the
coordinates carefully, and found that they did not in fact describe a Cs
structure-- close, but not exactly, and Gaussian 94 spotted the
difference.  If you haven't already done so, check to make sure that the
cartesian coordinates show reflection symmetry EXACTLY.

Best regards,
Dale 

Dale Braden
Department of Chemistry
University of Oregon
Eugene, OR 97403-1253
[email-masked]