To summarize, we are assuming that: (1) the energy of an electron in an isolated C(2p"z") orbital is formula_86; (2) the energy of interaction between C(2p"z") orbitals on adjacent carbons "i" and "j" (i.e., "i" and "j" are connected by a σ-bond) is formula_87; (3) orbitals on carbons not joined in this way are assumed not to interact, so "formula_88" for nonadjacent "i" and "j"; and, as mentioned above, (4) the spatial overlap of electron density between different orbitals, represented by non-diagonal elements of the overlap matrix, is ignored by setting formula_89, "even when the orbitals are adjacent".