Study of structures, energies and vibrational frequencies of (O2)n+ (n = 2-5) clusters by GGA and meta-GGA density functional methods

The more stable ground state structures of gaseous phase oxygen cluster cations, (O2)n+ (n = 2-5), have been found to have point group symmetries D2h, D3h, D4h, and D5h for O4+, O6+, O8+ and O10+, converged to quartet (S = 3/2), sextet (S = 5/2), octet (S = 7/2) and dectet (S = 9/2) potential energy hypersurfaces, respectively by using M06-2X/6-311++G(3df,2pd) level of theory. Harmonic vibrational frequencies and dissociation energies for these structures have also been discussed. Other competitive structures for these clusters have also been discussed at the same level of theory.