Equation ( ) is conceptually appealing for it represents a union of sorts between two historically disparate frameworks for analyzing electronic structure. On one hand, the direct topological partitioning of the electron density through the QTAIM, and, on the other hand, Molecular Orbital (MO) theory. The latter connection can be made because the average electron energy 𝜒̅ can be approximated as an average energy of occupied orbitals, the electronic eigenvalues of a 1-determinant wavefunction,