The existence of single-wall carbon nanotubes (SWNTs) in organic solvents, in the form of clusters, is discussed. A theory is developed based on a bundlet model for clusters, describing the distribution function of clusters by size. The phenomena have a unified explanation in the bundlet model of clusters, in accordance with which the free energy of an SWNT, involved in a cluster, is combined from two components: a volume one, proportional to the number of molecules n in a cluster, and a surface one proportional to n 1/2 . The bundlet model for clusters enables describing the distribution function of SWNT clusters by size. The droplet model is formally analogous to the one for fullerene clusters. From purely geometrical differences, the models predict different behaviors. Single-wall carbon nanocones (SWNCs) of various disclinations are investigated via energetic and structural analyses. Several SWNC's terminations are studied, which are different among each other because of the type of closing structure and the arrangement of them. The SWNC packing efficiencies, and interaction-energy parameters, are intermediate between the ones of fullerene and SWNT clusters; an in-between behavior is expected. However, SWNC properties are calculated closer to those of fullerene and more distant from those of SWNT. FIGURE 3. SWNT-SWNH interaction energy with its surroundings in cluster volume or surface.FIGURE 4. Temperature dependence of solubility of C 60 -SWNH (droplet)/SWNT (bundlet). TORRENS AND CASTELLANO 568 INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY