Following previous work, up to 23 lowest-energy virtual orbitals of the Hartree-Fock calculation were selected, and orbitals within this subset were grouped by symmetry and Boys-localized 68 within each symmetry. Likewise, up to 23 highest-energy doubly occupied orbitals were also grouped by symmetry and Boys-localized within each symmetry. These two sets of localized orbitals (and the one singly occupied orbital, when present) were then considered as candidates for the active space. Next we describe how we ranked the localized orbitals.