From korkin@qtp.ufl.edu  Fri Feb 14 17:23:13 1997
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From: Anatoli Korkin <korkin@qtp.ufl.edu>
Reply-To: Anatoli Korkin <korkin@qtp.ufl.edu>
Subject: Re: CCL:G:Singlet Oxygen with UHF
To: chemistry@www.ccl.net
Cc: qiang@euch4e.chem.emory.edu, bartlett@qtp.ufl.edu, balkova@nadn.navy.mil,
        perera@qtp.ufl.edu, BOYD@AC.DAL.CA, pvrs@organik.uni-erlangen.de
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> 
> > Hi,
> > can anybody please tell me how to compute the lowest singlet state
> > of the oxygen molecule (singlet-Delta_gerade, 0.984 eV above the
> > triplet-Sigma_gerade ground state) with the UHF method ? 
> 

The ACES II program has two-determinat coupled-cluster method. 
You will get in a consistent way both right energies and wave functions
for the lowest triplet and both singlet states. The type of the 
reference function is not important if you do not care about a
spin contamination. Technically you can use the orbitals from ROHF
or UHF solution for the triplet oxygen.

For theory look: A. Balkova, R.J. Bartlett, J. Chem.Phys. Lett., 1992,
193, 364, and references therein.

For some recent examples: A.A. Korkin, A. Balkova, R.J. Bartlett,
R.J. Boyd, P.v.R. Schleyer, J. Phys. Chem. 1996, 100, 5702.

To get the ACES program contact Prof. Rodney J. Bartlett (bartlett@qtp.ufl.edu)
or Dr. Ajith Perera (perera@qtp. ufl.edu).

Anatoli Korkin


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