Subject: CCL:MCSCF active space selection

From: "Dominik Horinek" <[email-masked]>
Date: Mon, 8 Jul 1996 18:27:55 -0600

Dear Netters:

I need accurate ground state energies for the HOCl molecule
in regions of the potential energy surface far away from the
equilibrium geometry.

I tried CASSCF with the D95+* basis set using Gaussian94.
With every set of CAS-orbitals the calculation was aborted
due to a wrong active space, I got warnings like:

"large rotation I, J ..."
with I and J variing over the full range of MO's.

In my calculation the active space should consist of all
orbitals which are affected by a special distorsion, say the cleavage
of the Cl-O bond, but choosing those orbitals results in the errors
cited above.

After a look at the molecular orbital coefficients it seems to me
that the only complete active space consists of all orbitals.

Any suggestions how to select a right active space in this case?

I would be glad to receive additional pointers to introductory
texts on MC-SCF.

Thanks in advance,

Dominik

P.S.: I already searched the CCL archive but found nothing
      really apropriate.

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Dominik Horinek
Institut fuer physikalische und theoretische Chemie
Lst. Prof. Dick
Universitaet Regensburg
Universitaetsstr. 31
93053 Regensburg
Deutschland
email: [email-masked] 
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