I working on CASSCF/GUGA. C4v symmetry.
Could you explain negative value for ISTSYM? I found, for $drt group=c4v $end i can setup 0,1,2,3,4 values for istsym. Also i can setup -1,-2, -4 -5, -6. -3 doesn't work. In general, is it possible to request two different states. For example A1 and E? Thus, for istsym=0, istsym=1 and istsym=3 two possible states will be considered: A2/B2, A1/B1, A2/B2.
Thank you very much.