[molpro-user] FCI converges to wrong excited state?

Lorenzo Lodi l.lodi at ucl.ac.uk
Wed Jan 21 16:51:57 GMT 2015

Thanks, Peter... In any case I found a workaround which is enough in my
After the state-averaged CASSCF I do a second CASSCF run specifying only
the state I want (in my case the singlet Sigma+) but keeping unchanged
the core orbital from the first CASSCF by using the FROZEN keyword.
Doing FCI on top of the second CASSCF gives the correct 1 Sigma+ state

Kind regards,


On 21/01/15 09:09, Peter Knowles wrote:
> Dear Lorenzo,
> I'm afraid the eigensolver in FCI is not as sophisticated as those in MCSCF and MRCI. Once it has generated a trial vector - which in this case happens to be singlet Delta - it then works in a Krylov space generated from that vector, and you will never reach vectors of different symmetry except perhaps by numerical accident following round-off.
> Best regards,
> Peter 

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