Subject: EOM IP

From: Zsolt Szekeres <[email-masked]>
Date: Tue, 7 Dec 1999 21:59:39 +0100 (CET)

Hi,

  I've been calculating ionization potentials using the EOM technique.
Considering the simplest ionization operator, one yields the generalized
eigenvalue equation of the generalized Fockian:

Fc=ePc,

where P is the first-order density matrix and e is the ionization
potential. Once the generalized eigenvalue problem of F is solved,
several e's appear. Some of these are valid solutions, some of them
are completely irreal. 
   My question is how to tell which solutions are proper, ie. how to 
tell apart the "good" and the "bad" solutions. An answer to this question
would be the choice of the norm of the Feyman-Dyson amplitudes belonging
to the e's. 
   This one seems to be a good choice till one attempts to do calculations
in larger basis sets (cc-PTVZ). /The applied wavefunction is geminal./
Unfortunately, these numbers fail to work at some point: these norms give
you not only large (close to 1) and small (close to 0) numbers, but also
numbers around 0.5 ...
   Any detailed help or reference would be appreciated.

Zsolt Szekeres
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