Structures and vibrational frequencies of the carbon molecules C2-C18 calculated by density functional theory

A density functional study of the molecular structure and vibrational frequencies of the linear and planar monocyclic isomers of the C n (2≤n≤18) series was performed. A gradient corrected energy functional of the Becke-Perdew type and a triple-ζ valence basis with a polarization function was employed. The results show that for n≤9 the linear chains are generally more stable than the ring structures. A possible exception is C 6 where, in contrast to previous studies, the two forms were computed to be near isoenergetic. For n≥10 the cyclic structures dominate; however, only the C 10 , C 12 , and C 14 monocyclic planar rings were found to represent minimas on the energy surface. Excellent agreement for the computed vibrational frequencies with experiment-whenever available-was found