Subject: symmetry in G98

From: Meike Reinhold <[email-masked]>
Date: Wed, 13 Oct 1999 17:02:30 +0100

HI All,

I have asked this question already some time ago, but I am still not
totally clear about the use of symmetry in Gaussian.
Maybe somebody would be so nice to point me to a good reference or so.
The question is:
I want to calculate the geometry and the frequencies of a highly
symmetric molecule (in this case D6H). The variables have been chosen in
order to be D6H, this means the bond length, etc. which generate the
symmetry have all the same variable.
If I use only the default input without the symmetry keyword, than G98
recognizes the symmetry, but during the optimization it aborts the
calculation because the molecule has no longer D6H symmetry (this is
what I make out from the error message).
Symmetry saves time and helps in a lot of ways.
COuld somebody explain me what exactly happens in simple words?
Thanks,
Meike Reinhold
Ph.D. Student
Chemistry Department 
York University
UK

---

From: "Qiang Fu" <[email-masked]>
Date: Wed, 13 Oct 1999 09:15:17 -0700

Dear Meike Reinhold,

I had the similar problem before.  During the optimization, G98 tries to
change the orientation of the molecule, which results abnormal ending of the
calculation.  Thanks to Dmitry from Emory, I can overcome this problem now.
I hope the email from Dmitry will be helpful to you.

later

Qiang Fu

-----Original Message-----
From: Dmitry Khoroshun [mailto:[email-masked]]
Sent: Sunday, May 02, 1999 10:26 PM
To: [email-masked]
Subject: symmetry

Hello!

I suggest you explore Gaussian's IOP's. They are available in Technical
information on www.gaussian.com . Particularly, you may want to
set iop(2/16=2) or iop(2/16=3), which governs what happens
when the group or orientation changes (default is to bomb off). Also,
you may want to increase the difference criteria determining is structure
is symmetric (iops 2/17 and 2/18).

Sincerely,
Dmitry Khoroshun
[email-masked]

HI All,

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