Abstract: At the level of ab initio 3-21G, the equilibrum geometries of linear carbon clusters C_n~e(n≤8, |e|≤2) have been optimized by using an energy gradient method. Ionization potentials obtained display odd-even alternations with the increase of carbon atoms in clusters. Based on ab initio calculations, occupied canonical molecular orbitals(CMO) are localized with Boys local-ization method. Analysis of the properties of LMOs shows that there are two-centre σ and π bonds, multi-centre σ and π bonds and bending bonds in the linear carbon clusters C_n~e. Such as this variety of bonding types could be considered as the character of bonding behavior for small carbon clusters. Furthermore, the relations between bonding properties and stabilities are discussed. It is shown that the conjugation of chemical bonds plays a significant role for the stabilities of small carbon element clusters.

Key words: Carbon element clusters, Ionization potentials, Localization, Chemical bonds