THE NATURE OF THE CARBON-CARBON BOND IN THE C2 AND C2H2 MOLECULES

The alternative description of the carbon-carbon bond in the C2 and C2H2 molecules in terms of sigma/pi or bent ''banana'' orbitals analyzed here within the framework of the spin-coupled method. In particular, the first all-valence electron calculations on both models are presented. Comparison with previous work on these molecules demonstrates the importance of correlating all the valence electrons, especially for the C2 molecule which shows a change in relative stability of the two bond models when nonbonding electrons are correlated.