Theoretical study of C2 and C2-
Abstract
Potential energy curves of the ground states of C2(X 1Σg+) and C2-(X2Σg+) have been calculated using SCF, MCSCF, and CI methods. Close agreement with experimental dissociation energies, bond lengths, and spectroscopic constants is obtained by a CI calculation including all single and double excitations from the restricted Hartree-Fock configuration, with corrections for the quadrupole excitations estimated by a formula due to Davidson. The restricted Hartree-Fock method overestimates the electron affinity of C2, giving a value 4.33±0.02 eV to be compared with the experimental value of 3.54±0.05 eV. The effect of higher excitations on calculated electron affinity has been investigated, and some general conclusions regarding the computation of molecular electron affinity have been drawn. © 1980 American Institute of Physics.