Structures, stability, and growth sequence patterns of small homoclusters of naphthalene, anthracene, phenanthrene, phenalene, naphthacene, and pyrene

Growth sequence patterns of molecular clusters have not been well elucidated. To examine structures of planar-molecule clusters, naphthalene, anthracene, phenanthrene, phenalene, naphthacene, and pyrene clusters with up to 10 molecules were theoretically investigated with the all-atom OPLS potential. The global-minimum geometries of the naphthalene dimer, trimer, and tetramer are consistent with the experimental data, suggesting that the model potential is useful for predicting the cluster geometries. The growth sequence patterns of the naphthalene, anthracene, phenanthrene, and naphthacene clusters are based on herringbone structures whereas the structures of the phenalene and pyrene clusters are amorphous. The magic numbers of the clusters are 7 or 8 except for the phenalene clusters. These numbers are used to discuss structural motifs of the clusters.