Local spin analysis and chemical bonding.

The electronic structure of main-group diatomic molecules is discussed in the light of local spin analysis. A deep investigation into the origin of local spins and their coupling is presented. It is shown that the presence of significant local spins in bonded molecules flags deviations from the classical bonding prototypes. For the notorious example of the C2 molecule, the local spin analysis indicates that its ground state has all ingredients to be categorized as a diradical.