Wikipedia - Metodo di Hückel Hückel molecular orbital (HMO) theory

https://doi.org/10.1351/goldbook.HT07035
The simplest @M03996@ theory of π-conjugated molecular systems. It uses the following approximations: π-electron approximation; LCAO representation of the π-molecular orbitals; neglect of electron-electron and nuclear-nuclear repulsions (in fact, the assumption that these cancel). The diagonal elements of the effective Hamiltonian, coulombic integrals, and the off-diagonal elements, @R05326@ integrals, (accounted for only directly bonded atoms) are chosen as empirical parameters, all overlap integrals being neglected.
Source:
PAC, 1999, 71, 1919. (Glossary of terms used in theoretical organic chemistry) on page 1944 [Terms] [Paper]