关键词: 共轭, 电子态, 成键, 不可约表示, 相关图, 分子模型, 休克尔分子轨道, HUCKEL-HUBBARD近似

In order to contrast the HMO theory (HMO) with a simple valence bond theory (Heisenberg-Dirac model), which are two opposite asymptotic limit cases of the Hubbard model, Hubbard problems have been solved for four sites systems with four electrons. The Hueckel-Hubbard correlation diagrams, where employs a parameter: U/t, have been obtained for these system. From correlation diagrams some interested results have been deduced in detail.e

Key words: CONJUGATION, ELECTRONIC STATES, BONDING, IRREDUABLE REPRESENTATION, CORRELOGRAM, MOLECULAR MODEL, HUCKEL MOLECULAR ORBITAL