Comparison of stabilities of group-14-atom-terminated linear carbon clusters ECn/ECn+/ECn− (E = C, Si, Ge, Sn, or Pb; n = 1-10) on the parity alternation effects

A comparative investigation has been carried out on the group-14-atom-terminated linear carbon clusters ECn/ECn+/ECn- (E = C, Si, Ge, Sn or Pb; n = 1-10) using density functional theory (DFT-B3LYP) method in conjunction with 6-311+G* (for C, Si and Ge) and TZP+ (for Sn and Pb) basis sets. For each linear ECn/ECn+/ECn- species, the low-lying electronic states, total energies, and incremental binding energies are considered. The incremental binding energy diagrams show that, terminated by different group-14-atom E, ECn/ECn+/ECn- clusters exhibit similar parity alternation effects in their stabilities, i.e. both neutral ECn and anionic ECn- clusters have obvious even-odd alternation in the cluster stability, with the n-even members being much more stable than the corresponding odd n − 1 and n + 1 ones (except CCn-), while for cationic ECn+, the alternation effect is less pronounced, except for smaller EC+,EC2+,EC3+ and EC4+. On the other hand, when heteroatom E goes from C to Si to Ge to Sn to Pb, the amplitude of the alternation is very similar for neutral ECn, but larger and larger for anionic ECn- (except CCn−). Systematical investigations on these clusters' electronic distributions and orbital character find that the parity effects in their stabilities are attributed to the numbers of their valence π electrons and the extent of the orbital overlapping between E and C atoms.