An ab initio Effective Core Potentials（ECPs） Calculation on Group ⅣA Tetramethyl Compounds

The electronic structures and Koopmans ionization energies of Me₄M （Me=CH₃, M= C,Si,Ge,Sn,Pb） were calculated using PS-HONDO method. Koopmans ionization energies calculated are in agreement with the experimentally observed values and Penning ionization electron spectra reported. The characteristics of Photoelectron spectra were discussed with orbital levels and orbital components of Me₄M. A theoretial explaination was given for the particularities of spectra terms 2α₁ of Me₄Si and Me₄Sn.