you are absolutely right. As triplet O2 has exactly
half-filled high-spin open-shell, ROHF orbitals should work as well.
On the other side, for NO molecule they are not symmetric so one
may use ROHF orbitals of NO+ molecule instead.
>>2. Initially, it is better start with RHF orbitals of closed-shell
>>axially-symmetric ion or neutral molecule. This will give you
>>starting orbitals of proper symmetry. E.g., RHF orbitals of singlet
>>N2 in ground state are symmetric while RHF orbitals of singlet O2 are not!
>Dear Alex. My problem is that in the case of O2 the ground state is triplet. That was the reason why I have started with ROHF orbitals. But probably it was my mistake, and the choise that you suggest is
>>For O2, you would need RHF orbitals of O22+ system.