Elucidation of the structural characteristics of the isovalent species Li[CO] and Li[CS] by ab initio calculations

We have performed ab initio CISD(+corrections) calculations on the valence isoelectronic molecules Li[CO] and Li[CS] using large basis sets. The Li-CO, Li-OC, LI-CS and Li-SC (II)-I-2 states are bound with respect to Li P-2 by 38, 8, 70 and 41 kcal/mol, respectively. With the exception of LiCS C-2 Sigma(+), which presents a shallow minimum of 4 kcal/mol, all the relevant (2) Sigma(+) states examined are repulsive. Full potential energy curves are also presented for the most interesting of the states.