Subject: CASPT2 using Gaussian98

From: Juan Pablo Senosiain <[email-masked]>
Date: Fri, 5 Oct 2001 11:07:07 -0700 (PDT)

Dear colleages,

I performed CASSCF and CASPT2 calculations on O2 molecule using the
cc-pvTZ basis set and  2 active  spaces: 6elect, 4 orbitals (i.e. the
degenerate pi system) and 8 electrons, 6 orbitals (sigma + sigma* + pi
system).

The two CASSCF calculations look reasonable, but the CASPT2 optimisations
break the symmetry of the pi orbitals, resulting in HOMOs localized on a
single atomic centre, and fail to converge. Does somebody have an insight
on why this happens?

many thanks.

 juan pablo
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  J u a n   P a b l o   S e n o s i a i n   P e l a e z

	Materials  Science  and  Engineering
	S t a n f o r d  U n i v e r s i t y
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