Theoretical Study of AlCn, AlCn+, and AlCn- (n = 1−7) Clusters

Abstract

AlCn, AlCn+, and AlCn- (n = 1−7) clusters have been studied by means of the B3LYP density functional method. Results of their equilibrium geometries, electronic energies, dipole moments, and vibrational frequencies are reported. The energy calculations show that the open-chain linear or quasi-linear isomers with the aluminum atom bound to the end of the carbon chain are the most stable geometry in all cases. For the AlCn clusters the electronic structure is predicted to be a doublet, with the only exception of AlC. In the AlCn+ species, the electronic ground state was found to be alternately a singlet for odd n or a triplet for even n, again with the exception of the first member of the series, and in the AlCn- clusters the opposite was found. From the binding energies we can deduce an even−odd parity effect, with n-even clustering atoms being more stable than those with odd ones in the neutral and anionic clusters, whereas in the cations this effect is reversed. The ionization potentials (IP) and electron affinities (EA) also computed show an even−odd alternation with n-even clusters presenting both higher IP and EA than n-odd ones.