the ISPIN option works only with iterative Davidson eigensolver.
With CASSCF(2,2) and alike, Hamiltonian matrix is tiny and is
diagonalized directly using one of available diagonalization
routines rather than iteratively, so that the ISPIN option is
My guess is that you set NSTATE to 2 and got two states,
namely lowest singlet and lowest triplet. This is why program
complains (as it needs two singlet states). Use NSTATE=3 and
you'll get two singlets and a triplet state.
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?