Structures and stabilities of non-linear VCn+/− (n = 1-8) clusters

A theoretical study of the different fan and cyclic isomers of VCn+/− (n = 2-8) clusters has been carried out. Predictions for different molecular properties, such as electronic energies, harmonic vibrational frequencies or rotational constants, have been made using the B3LYP method with different basis set including effective core potentials, ECPs. In general, fan and cyclic structures have been predicted to prefer triplet ground states. The stability of fan and cyclic clusters as a function of the size has been discussed in terms of the incremental binding energies. For cationic systems a clear even-odd alternation in stability is found, n-even clusters being more stable than n-odd ones. This parity effect is also found for the first members of the fan isomers of VCn−, whereas for cyclic VCn− structures the stability decreases along the series. It is also found that VCn+ systems with n < 5 prefer fan structures over linear ones, whereas for n = 5-7 the open-chain isomers are the most stable and for n = 8 cluster the cyclic structure is the most stable. Anionic vanadium-doped carbon clusters with n ≤ 5 prefer fan structures, whereas for n > 5 n-even clusters prefer open-chain structures and for VC7− the cyclic structure is the most stable.