[molpro-user] How to restrict external excitations

[Fernando D. Vila]

Hello everybody,

   I'm trying to compute some core-ionization energies. Right now I'm using 
the following input for ci:

{rhf;
wf, 14, 1, 0
occ, 5, 1, 1, 0
}

{ci;
occ,    7, 3, 3, 2
core,   1, 0, 0, 0
closed, 0, 0, 0, 0
wf, 13, 1, 1;
restrict, 1, 1, 2.1;
state,1, 1;
thresh, printci=0.0050;
noexc;
}

This gives me what I want: The restrict card puts a permanent hole in the 
2nd orbital, which corresponds to a core orbital in the system I have. The 
noexc option limits the space to those CSFs with a hole and the lowest 
state in the reference space is the core-ionized state. But obviously this 
doesn't include correlation beyond that included in the reference space 
and the core-ionization energy is quite bad.

The problem is that, as expected, when I remove the noexc option there are 
single and double external excitations into the core-ionized orbital which 
correspond to much lower roots (the valence ionized states). Thus the CI 
solver flips the roots and the overlap with the reference is too low.

Now, to my question: This could be solved if I was able to restrict the 
occupation of the core orbital not just in the reference space, but also 
in the S and P spaces. Is there any way this can be done?

I would truly appreciate any insights into this.

Best regards, Fer.

Ubi dubium ibi libertas.
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Fernando D. Vila                Voice    (206)543-9697
Department of Physics           Fax      (206)685-0635
University of Washington        E-mail   fdv at u.washington.edu
Seattle, WA 98195, USA          WWW      http://faculty.washington.edu/fdv
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