Electronic Structure of Cobalt Carbide, CoC

The ground and 18 low lying excited states of the diatomic molecule cobalt carbide, CoC, have been examined by multireference variational methods (MRCI) combined with quantitative basis sets. All calculated states are bound and correlate adiabatically to the ground-state atoms, Co(a4F) + C(3P). We report complete potential energy curves, equilibrium bond distances, dissociation energies (De), spectroscopic constants, electric dipole moments and spin-orbit splittings. The bonding character of certain states is also discussed with the help of Mulliken distributions and valence-bond-Lewis diagrams. We are practically certain that the ground state is of 2Sigma+ symmetry with a state of 2Delta symmetry lying less than 3 kcal/mol higher, in agreement with the relevant experimental findings. Our best estimate of the X 2Sigma+ dissociation energy is De(D0) = 83(82) kcal/mol at r(e) = 1.541 A, 0.02 A shorter than the experimental bond length.