Structure and Stability of Small NaCn, NaCn+, and NaCn- Clusters: A Theoretical Study

Abstract

NaCn, NaCn+, and NaCn- (n = 1−8) open-chain and cyclic clusters have been studied using the B3LYP method. Predictions for several molecular properties that could help in possible experimental characterization, such as equilibrium geometries, electronic energies, dipole moments, and vibrational frequencies, are provided. NaCn open-chain clusters are predicted to be linear with 2Π lowest-lying states, whereas for both cationic and anionic clusters the lowest-lying state alternates between singlet and triplet. Also, cyclic neutral clusters have doublet lowest-lying states. An even−odd alternation in stability is observed for both cationic and anionic cyclic clusters, whereas no parity effect is observed generally for the corresponding neutrals. Ionization potentials and electron affinities of NaCn cyclic clusters also exhibit a clear even−odd parity effect. It is generally observed that removing an electron destabilizes the cyclic isomer, whereas adding an electron generally increases the stability of the cyclic species. NaC2 and NaC3 are predicted to have cyclic ground states, whereas most anionic clusters up to n = 8 prefer also a cyclic arrangement.