In addition to quantities derived from the 2-RDM and its cumulant, and ⟨S 2 ⟩ U CCSD , we would like to explore an additional metric defined here. The Born-Oppenheimer Hamiltonian can be written as Ĥ = T + Ven + Vee + Vnn = Ĥ1e + Vee + E nn , where T is the kinetic energy operator, Vee = pqrs V pqrs c † p c † q c s c r (V pqrs are two-electron integrals), and E nn is a constant energy shift. The first candidate metric is motivated by the large U/t limit of the Hubbard model, which is widely accepted by physicists to exhibit strong correlation, and also the Virial Theorem. One possible analog for molecules is the ratio: