Evidence for a solid phase of dodecahedral C 20

Evidence is presented for the formation of a solid phase based on the smallest fullerene, C20, in thin diamond-like carbon films deposited by ultraviolet laser ablation from diamond onto nickel substrates at room temperature in the presence of 10-4 torr of cyclohexane or benzene. Laser desorption mass spectrometry from the films shows the presence of C 20, C21 and C22 species, while micro-Raman spectroscopy and electron diffraction from selected particles together with first principle density-functional calculations, indicate a cubic solid with dodecahedral C20 cages as building blocks. Unlike solid C 60 and fully protonated C20, which are bound by van der Waals forces, the proposed structure is stabilized by linking of the C 20 dodecahedra, with bridging carbon atoms at interstitial tetrahedral sites to form a face-centered-cubic lattice with 22 carbon atoms per unit cell. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003