[molpro-user] how to handle singlet diradical?
H. -J. Werner
werner at theochem.uni-stuttgart.de
Sat Apr 22 14:15:17 BST 2006
It is not possible to to open-shell singlets with rhf or uhf.
Only high-spin states (single Slater determinants) are possible.
Use mcscf for open-shell singlets!
On Sa, 22 Apr 2006, MHT wrote:
>I met the same problem as following, please see "OCC"
>"The total number of orbitals must be equal to (elec+spin)/2"
>does this still work for singlet diradical: _up_, _down_,
> * To: molpro-user at xxxxxxxxxx
> * Subject: [molpro-user] singlet diradical
> * From: ghoffman <ghoffman at xxxxxxxxxxxx>
> * Date: Mon, 13 Jun 2005 10:14:09 -0400
> * Sender: owner-molpro-user at xxxxxxxxxxxxxxxxxxxx
>I need some helpful advice for performing a clculation on a singlet
>diradical. This is a triatomic species with 16 electrons and Cv symmetry.
>The two unpaired electrons are in orbitals of different symmetry
>(1=totally symmetric and 2=antisymmetric with respect to reflection in the
>symmetry plane). Therefore, the symmetry of the electronic state is 2.
>Because this is a singlet state then, the command for the Hartree-Fock
>calculation ought to be:
>The negative sign, according to the manual, designates that the spins of
>the two unpaired electrons are opposed. However, with this input (and
>just about every other one I could think of), the following error message
>is returned when the calculation crashes:
> SYMMETRIES FROM ORBITAL RESTRICTIONS AND WF CARD NOT CONSISTENT: 2 2
>MS2= 0 NOPEN= 2
> ERROR EXIT
> CURRENT STACK: MAIN
>Surely, somebody out there has performed calculations on singlet
>diradicals. How does one get Molpro to understand the desired electron
>Thanks in advance.
>Gerald J. Hoffman
>Assistant Professor of Chemistry
>Edinboro University of Pennsylvania
>Edinboro, PA 16412
>ghoffman at xxxxxxxxxxxx
Prof. Hans-Joachim Werner
Institute for Theoretical Chemistry
University of Stuttgart
D-70569 Stuttgart, Germany
Tel.: (0049) 711 / 685 4400
Fax.: (0049) 711 / 685 4442
e-mail: werner at theochem.uni-stuttgart.de
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