in C1, all irreps of D2h group belong to a totally symmetric
irreducible representation (as C1 group has only this irrep).
In particular, this means that with C1 group in effect
you can find states of any available symmetry types according to the
native classification of D2H group (which by itself has eight
different irreps and hence there are eight symmetry types). They all will be
labeled as A1 within C1 group.
With D2h group in effect, by default you will be limited to totally-
symmetric states of D2h group (of course you can change symmetry type
using istsym keyword).
Hope this helps.
On Tue Oct 4 '11 6:04am, Solntsev Pasha wrote
>Dear Alex and all FF users.
>I have a problem with performing SA-CASSCF(4,4) of molecule with D2H symmetry. I use D2H symmetry in $drt group=d2h $end and i don't see ANY single electron excitation (nstate=8, wstate(1)=1,-0). Opposite, if i use no symmetry at drt group (group=c1) all four single electron excitations go up. Symmetry in $data is D2H. The same thing with ALDET code. Such behavior is strange for me, however, i am not an expert and any explanation or advice will be very helpful.
>If you need full input file i am ready to provide it.
[ This message was edited on Tue Oct 4 '11 at 9:53pm by the author ]