ITERATIVE EXTENDED HUCKEL METHOD (IEHM)

The iterative extended Hückel method for σ-electrons, analogous to the ω-technique for π-electrons, is used to calculate wave functions for BH4-, NH4+, CH4, C2H6, B2H6, C2H4 and C6H6. Results are compared with the simple extended Hückel method and with published selfconsistent field molecular orbital wave functions. It is found that iterating the extended Hückel method does not always lead to improvements in the wave function but that some improvements are found particular for ionic molecules. It is suggested that the reason for the failure of the iterated method is the neglect of terms due to charges on adjacent atoms. © 1968 Springer-Verlag.