Role of Angular Electron Pair Correlation in Stabilizing C 60 2

A pseudo-potential that was successfully employed in an earlier study by the Compton group is used to describe the binding of a single electron to a C60 molecule to form C60 . Then, the interaction of a second electron with the C60 anion is treated in two manners. First, as performed in the earlier Compton study, a mean-field (i.e., Hartree–Fock) approach is used to estimate the C60 -to-C60 2 energy difference for the singlet state of the dianion and, much as in the earlier study, this dianion is predicted to be unstable by 0.4 eV. Second, for this same singlet state, a configuration interaction wave function is employed that allows for the angular correlation of the two excess electrons, allowing them to avoid one another by moving on opposite sides of the C60 skeleton. The energy of the dianion is lowered by 0.3 eV when angular correlation is included, suggesting that the singlet dianion is unstable with respect to electron loss by only 0.1 eV. A Coulomb barrier ( 1 eV high) and angular momentum barriers then combine to trap electrons of singlet C60 2 from detaching, thus producing the very long observed lifetimes. In addition, the energy of the lowest triplet state of C60 2 is also discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 106: 507–513, 2006