The combination of ISPIN=0 and NSTGSS will only filter out states with an odd multiplicity, so it could be possible that states with higher even multiplicities are still present in the number of states requested with NSTATE. Also, it could be that there are many states of odd multuplicities lying between the S0 and S1 states -- in this case, NSTGSS is simply not set high enough (remember that filtering with ISPIN/NSTGSS takes place prior to optimization of the CI coefficients, at a time where the state order is most likely incorrect).
Edit: I looked over the fact that the active space size is merely (2,2).
On Fri Feb 24 '17 2:18pm, GrEv wrote
>I have a question related to a SA2-CAS(2,2) calculation using cistep=ALDET and ISPIN=0.
>I am interested in two singlet states, S0 and S1. Even with NSTGSS=4
>the calculation crashes with the error:
> ***** ERROR *****
> THIS RUN FOUND 1 CI EIGENVECTORS WITH S= 0.00,
> BUT YOU REQUESTED STATE AVERAGING OF 2 ROOTS.
> PLEASE EXAMINE YOUR CHOICE OF -NSTATE- INPUT DATA.
>So, I wonder if cistep=ALDET can be used in such a case, or only cistep=GUGA works here?
[ This message was edited on Sun Feb 26 '17 at 4:19pm by the author ]