title: Dimerization of defect fullerenes and the orientational phase transition in oxidized C60 fullerite.
abstract: Oxidized fullerite was obtained by heating a fullerite sample intercalated with oxygen, (O2)0.44C60, up to 300 degrees C. Orientational phase transitions in the oxidized fullerite are studied using differential scanning calorimetry (DSC) and have been found to possess a specific enthalpy whose value is lower by 25% than in the initial (O2)0.44C60 sample. In order to find possible reasons for hindrance to the buckyball rotations, we performed optimizations of defect buckyball fullerenes C60-n with different distributions of vacancies along with the dimers C60-n-C60-n and C60-C60-n for n = 1-4 using density functional theory with generalized gradient approximation. We found that the dimerization energy ranges from 1.07 eV (C58-C58) to 6.56 eV (C56-C56) and from 1.81 eV (C60-C58) to 4.29 eV (C60-C56), respectively. The formation of such dimers, which could in addition interact with defect buckyball cages and form larger aggregates, is to be related to the lowering of the orientational transition enthalpy.
authors: Department of Physics, Florida A&M University, Tallahassee, Florida 32307, USA.
authors: G L
authors: GL
authors: Gutsev
authors: K G
authors: KG
authors: Belay
authors: C A
authors: CA
authors: Weatherford
authors: V N
authors: VN
authors: Vasilets
authors: E M
authors: EM
authors: Anokhin
authors: A V
authors: AV
authors: Maksimychev
authors: O V
authors: OV
authors: Val'ba
authors: V M
authors: VM
authors: Martynenko
authors: S A
authors: SA
authors: Baskakov
authors: E S
authors: ES
authors: Leskova
authors: Y M
authors: YM
authors: Shulga
mesh_terms: D003198:Computer Simulation; D019281:Dimerization; D037741:Fullerenes / Q000737:chemistry*; D008422:Materials Testing; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010084:Oxidation-Reduction; D044367:Phase Transition
chemical_list: D037741:Fullerenes; C069837:fullerene C60