From chemistry-request@ccl.net Thu Jul  9 18:46:41 1992
Date: Thu, 9 Jul 92 11:45:07 -0400
From: friedman@tammy.harvard.EDU (Dawn Friedman)
Subject: gaussian wavefunctions
To: chemistry@ccl.net
Status: R

  
  I'm a bit mystified by the output of the STABLE keyword in Gaussian 90.
Has anyone used this keyword to test the stability of their HF (especially UHF)
wavefunctions?  Once you've determined that your wavefunction _is_ unstable
with respect to one or more factors, and used the stable=opt option to get
a better wavefunction, what do you do next? For example, if the unstable
wavefunction was the result of an geometry optimization, is it possible to
get a better geometry from the better wavefunction in some way?  What do
you do with the better wavefunction other than admire it?  And what do the
various forms of instability "mean" in physical terms, if anything?
  
  Thanks,
  Dawn
  
  (friedman@tammy.harvard.edu)
  
p.s. to jkl:  thanks for letting us know.  It's always unpleasant to be the
bearer of evil tidings, or even moderately annoying tidings...