Electron propagator calculations on linear and branched carbon cluster dianions

Electron propagator calculations have been performed on linear carbon cluster dianions from C2−7 to C2−10 and on branched C2−7, C2−9, and C2−11 structures which have a central, tricoordinate carbon bound to three branches with alternating long and short bonds. The more stable, branched isomer of C2−7 has a positive vertical ionization energy, but the linear form does not. While linear C2−10 is stable with respect to electron loss, it is not possible to decide from these calculations whether linear C2−8 and C2−9 have the same property. There is evidence that better calculations would obtain bound C2−8 and C2−9 species. Vertical ionization energies of all branched dianions are positive. Feynman–Dyson amplitudes for dianion ionization energies display delocalized π bonding, with the two terminal carbons of the longest branches making the largest contributions.