Structures of small carbon clusters: Cyclic ground state of C6

Abstract

Accurate ab initio calculations have been performed to investigate the nature of the structures and energies of different C₆ isomers. The effects of polarization functions and electron correlation have been included in these calculations. A cyclic singlet structure with six π electrons (planar D_3h,¹A’) is found to be the ground state. The linear ³Σ⁻_g structure lies about 10 kcal/mol higher in energy. The heat of formation, ΔH°₀, of C₆ is estimated to be ∼281 kcal/mol.