Isomer Spectrum of Small Carbon Clusters

A theoretical method is developed to find isomers of cluster particles,and the isomer spectrum of carbon clusters C_n(n=3-44) is obtained. It is found that the isomers of 3-11 atoms are in either mono-ring or line shapes, while the isomers of 12-18 atoms show flat sheet shapes. As cluster size increases, bowl isomers become more (n>19) until cage isomers dominate the structures (n>27). Based on the isomer spectrum, results of a previous experiment are interpreted.