[molpro-user] singlet diradical

[ghoffman]

Hello,

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:

uhf;wf,16,2,0;occ,7,2;open,7.1,-2.2;

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 configuration?

Thanks in advance.

Gerry Hoffman



Gerald J. Hoffman
Assistant Professor of Chemistry
Edinboro University of Pennsylvania
Edinboro, PA 16412

814-732-2813

ghoffman at edinboro.edu