I need to do some frozen core correlated wavefunction calculations (CCSD, in the first instance). As part of the work I will need to determine precisely which orbitals are treated as frozen, and which are treated as active, in potentially complex molecules. I need to be quite sure I’m treating the right orbitals as frozen/unfrozen.
Is there an easy way to do this? My first guess would simply be to take the number of orbitals in the frozen cores - but perhaps this isn’t quite right.
And if not, is there a way to do it using internal methods?
Apologies if this is answered in the documentation.
Psi will always freeze the lowest energy occupied orbitals. Given a wavefunction, you can check how many electrons are in the frozen core by checking wfn.nfrzc(). If you just set frozen core to on, there should be one frozen electron for each electron in a non-valence orbital.