where h nuc is the nuclear-nuclear repulsion term, h pq and g pqrs are the 1-and 2-electron integrals, D I pq and d I pqrs are elements of the spinless reduced 1-and 2-particle density matrices of state |I⟩ (D I and d I respectively), and E ot is an on-top density functional of the density, ρ I , and on-top density, Π I . Summing all terms except the on-top functional equals the sum of the kinetic energy and classical electrostatic energy for the state.