摘要
1 Introduction Classical valence bond (VB) theory has made great success in the qualitative explanation of π conjugated systems. Nevertheless, modern VB theory is trying to make quantitative calculation to molecular structures. As one of the VB methods, the bonded tableau unitary group approach (BTUGA), which adopts the bonded tableaus as the VB-type many-
基金
Project supported by the National Natural Science Foundation of China.