Subject: Summary: CCL:a second question:BSSE/pseudo

From: Valentina Vetere <[email-masked]>
Date: Wed, 28 Jun 2000 11:03:27 +0200 (MET DST)

I received one answer, probably my question was not so clear...

I'm calculating BSSE correction on systems containing heavy elements.
To describe heavy elements I'm using ECP basis sets and core potentials.
Now, I have strange results because, on similar systems, BSSE can change from
2Kcal to 100Kcal..
So I'm not sure that the BSSE procedure (I mean using ghost atoms) is
theoretically right if ECP core potential are used.

If, as Doug Fox proposed, the procedure of removing core in the BSSE
calculation is theoretically right...what could be the problem?

I'm sure about the initial guess, every SP calculation is with conver=8..
So ..other suggestion?
thank you
valentina

-----FW: <[email-masked]>-----
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The only answer: Doug Fox
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  Vetere,

   I don't see other discussion but you may have direct responses.  I
agree that you need to remove the ECP when setting the ghosts.  I don't
see a problem with absence of the core since the point for the core
potential is to keep the valence electrons from collapsing into the region
about that nucleus.  Since you are removing both electrons on that atom
and the nucleus you will get the interaction between the remaining atoms
and those valence basis sets but no energy contributions.  When you 
reverse and compute the ECP portion you will get the corepotential 
contributions to the energy.

  I don't see where this is dramatically different than the other potential
errors in the CP process.  If someone else sees a bigger flaw let me know.

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