Subject: Incorrect wavefunction read in Gaussian98

From: "Mnr GA Venter" <[email-masked]>
Date: Tue, 24 Apr 2001 09:14:34 +0200

Hi

I am modeling first row transition metal ozone complexes with Gaussian98. At 
some point in my calculations I test for the stability of the wavefunction using 
the Gaussian98 command STABLE=OPT. When the program finds an 
instability it is corrected and a new, lower energy is calculated. I then attempt 
to optimize the geometry using the stabilized wavefunction as starting guess 
via the GUESS=READ command. The problem is that the program sometimes 
uses the new stabilized wavefunction’s energy and sometimes reverts back to 
the unstabilized wavefunction’s energy. It seems to do this indiscriminately. 
The only differences between the input files are the central atom and the 
associated multiplicity.

Thanks in advance.
Gerhard
[email-masked]

--------------------------------------
Gerhard Venter
Department of Chemistry
University of Stellenbosch
Private Bag X1
7602 Matieland
South Africa
---------------------------------------

---

From: "Phillip D. Matz" <[email-masked]>
Date: Tue, 24 Apr 2001 09:26:15 -0700

Hello,

When you attempt to read in the stable wave function you will need to set
the switch "nosymm" for the keyword "scf" and you will want to employ the
keyword/switch combination geom(allcheckpoint).  The geom(allcheckpoint)
will allow the wave function's guess multiplicity to be whatever noninteger
value the stable(opt) routine resulted.  Don't forget that the allcheckpoint
switch means that both the comment line and the charge, multiplicity line
are read from the checkpoint file. Here is an example:

%chk=d:\g98wcalcs\test.chk
#P RHF/STO-3G pop(full) gfinput iop(6/7=3) stable(opt)

Stability Test on Molecular Hydrogen with the STO-3G Basis

0 1
H
H 1 r1

r1 0.775

--LINK1--
%chk=d:\g98wcalcs\test.chk
#P UHF chkbasis pop(full) gfinput iop(6/7=3) guess(read) scf(nosymm)
geom(allcheckpoint)

This seems to work for me (credit goes to Joseph Ochterski at Gaussian, Inc.
for the solution).  Now I only wish that the results from a stability
calculation made more sense.  Just about every RHF wave function is instable
it seems, and just about every stable wave function has
spin-contamination...

Respectfully,

Phillip Matz
[email-masked]

----- Original Message -----
From: "Mnr GA Venter" <[email-masked]>
To: <[email-masked]>
Sent: Tuesday, April 24, 2001 12:14 AM
Subject: CCL:Incorrect wavefunction read in Gaussian98

> uses the new stabilized wavefunction's energy and sometimes reverts back
to
> the unstabilized wavefunction's energy. It seems to do this
indiscriminately.
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