Subject: wave function stability question

From: "Dale A. Braden" <[email-masked]>
Date: Mon, 9 Nov 1998 20:04:10 -0800 (PST)

Dear CCL,

I'm doing DFT calculations on an open-shell transition metal compound
using G94.  I saw that 3 of the virtual orbitals had negative eigenvalues:

 .....
Alpha  occ. eigenvalues   -0.20751  -0.14471
Alpha virt. eigenvalues   -0.03482  -0.01181  -0.01122   0.01779  0.03974
 .....
 
which I thought warned that the SCF had converged to an excited state, so
I performed a wave function stability calculation.  This reported that the
wave function was stable "under the perturbations considered", with an
eigenvalue of 0.0119 for the "stability matrix".  This was confusing, so I
have three questions: 

1) Am I correct that the stability calculation is NOT guaranteed to
recognize an excited state?

2) Are negative eigenvalues for virtual orbitals a SURE sign that an
excited state has been obtained?

3) In case I really still do have an excited state wave function, is the
only way to direct it towards the ground state to guess which orbitals
should be occupied, and then use guess=(read,alter) to fix their
occupations?  (I'd like to avoid hit-or-miss strategies!)

Best wishes to all,

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