RE: W:Symmetry breaking during CASSCF
- From: "Shobe, David"
- Subject: RE: W:Symmetry breaking during CASSCF
- Date: Fri, 8 Jul 2005 14:29:43 -0400
Jahn-Teller effect, perhaps? Does the D2h geometry have degenerate
orbitals which become non-degenerate once the symmetry is broken?
--David Shobe, Ph.D., M.L.S.
phone (502) 634-7409
fax (502) 634-7724
Don't bother flaming me: I'm behind a firewall.
From: Computational Chemistry List [mailto:chemistry-request|at|ccl.net] On Behalf Of Gustavo, L.C., Moura
Sent: Friday, July 08, 2005 7:35 AM
Subject: CCL: W:Symmetry breaking during CASSCF
Dear CCL Readers,
I have a planar conjugated organic molecule that, on paper, has D2h
symmetry. I am working with the hypothesis that the molecule is a biradical
singlet. I want to perform a CASSCF(2,2) on this molecule to estimate the
biradical character of this molecule. When I calculate the molecule with the
constraint that the molecule has D2h symmetry, the calculation has severe
convergence problems. If I remove this constraint, the molecule distorts to a
C2v symmetry and I obtain a biradical character ~20%. I checked the orbitals
being used for the CASSCF calculation and they look right (one nonbonding and
another slightly antibonding).
Is the situation described above correct? Can an organic molecule have such
a symmetry breaking as a result of a CASSCF calculation? Is the molecule really
a C2v system? Any suggestions are welcome.
Thank you very much in advance for your help.
Gustavo L.C. Moura
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