Nested Fullerenes on Graphite
A novel method of forming nested fullerenes by irradiation of carbon soot using the high energy beam in a 300-kV electron microscope.
fullerenes↗
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(abstract) Design and Testing of a Fullerene RF Ion Engine
Because of the large mass, low ionization potential and large electron impact ionization cross section, use of buckminsterfullerene (C 60 ) as a propellant might result in significant increases in ion engine efficiency over that obtained with xenon at low specific impulse. Consequently, an experimantal program to investigate the feasibility of using fullerenes as a propellant was initiated. To eliminate the possibility of hot cathode surfaces causing fragmentation, fabrication of a radio-frequency discharge chamber was pursued. Experimental results using the radio-frequency source will be presented.
fullerenes↗
An experiment to study fullerene formation under reduced gravity
The activity of the summer focused on the design and construction of key components of a carbon arc/inert gas reactor for fullerene production, that is suitable for reduced gravity experiments onboard the KC-135 aircraft. The apparatus will be configured for both floor-mount and free-floating operation providing access to reduction to 10(exp -2) and 10(exp -3) of normal respectively. It is planned to incorporate 'seat belt' restraints that will allow a safe transition from reduced gravity free-float to full gravity, at the end of the parabolic.
Wdowiak, Thomas J.↗
Molecular Static Third-Order Polarizabilities of Carbon-Cage Fullerenes and their Correlation with Three Geometric Parameters: Group Order, Aromaticity, and Size
Calculations were performed on the valence contribution to the static molecular third-order polarizabilities (gamma) of thirty carbon-cage fullerenes (C60, C70, five isomers of C78, and twenty-three isomers of C84). The molecular structures were obtained from B3LYP/STO-3G calculations. The values of the tensor elements and an associated numerical uncertainty were obtained using the finite-field approach and polynomial expansions of orders four to eighteen of polarization versus static electric field data. The latter information was obtained from semiempirical calculations using the AM1 hamiltonian.
Moore, Craig E.↗
Quantum Chemistry Study of Cycloaddition Pathways for the Reaction of o-Benzyne with Fullerenes and Carbon Nanotubes
Functionalization of fullerenes via the [2+2] cycloaddition reaction with o-benzyne has been demonstrated in the laboratory. In contrast, [2+4) cycloaddition products are formed when benzyne reacts with planar polycyclic aromatic hydrocarbons. Using density functional theory (DFT) calculations with Becke's hybrid functional and small contracted gaussian basis sets, we are able to reproduce these product preferences. The objective of this work is to explore the functionalization of carbon nanotubes. We have studied o-benzyne cycloaddition products with a [14,0] single-walled nanotube. We find both the [2+2] and [2+4] adducts to be stable, with the latter product being somewhat favored.
Jaffe, Richard↗
Toroidal Single Wall Carbon Nanotubes in Fullerene Crop Circles
We investigate energetics and structure of circular and polygonal single wall carbon nanotubes (SWNTs) using large scale molecular simulations on NAS SP2, motivated by their unusual electronic and magnetic properties. The circular tori are formed by bending tube (no net whereas the polygonal tori are constructed by turning the joint of two tubes of (n, n), (n+1, n-1) and (n+2, n-2) with topological pentagon-heptagon defect, in which n =5, 8 and 10. The strain energy of circular tori relative to straight tube decreases by I/D(sup 2) where D is torus diameter. As D increases, these tori change from buckling to an energetically stable state. The stable tori are perfect circular in both toroidal and tubular geometry with strain less than 0. 03 eV/atom when D greater than 10, 20 and 40 nm for torus (5,5), (8,8) and (10, 10). Polygonal tori, whose strain is proportional to the number of defects and I/D are energetically stable even for D less than 10 nm. However, their strain is higher than that of perfect circular tori. In addition, the local maximum strain of polygonal tori is much higher than that of perfect circular tori. It is approx. 0.03 eV/atom or less for perfect circular torus (5,5), but 0.13 and 0.21 eV/atom for polygonal tori (6,4)/(5,5) and (7,3)/(5,5). Therefore, we conclude that the circular tori with no topological defects are more energetically stable and kinetically accessible than the polygonal tori containing the pentagon-heptagon defects for the laser-grown SWNTs and Fullerene crop circles.
Han, Jie↗
Modeling Intermolecular Interactions in Nanotubes, Fullerenes and Graphite using a New Long-Range Potential
The cohesive energy and compressibility of strands of a single-wall nanotube rope has been computed using a new long-range potential energy function derived from accurate ab initio quantum chemistry calculations of the benzene dimer and calibrated for energetic and mechanical properties of graphite (at pressures up to 12 GPa). We also use this potential to calculate a variety of properties of carbon nanotubes (both single- and multi-wall) and fullerenes. Extensive comparisons are made with previously published potentials.
Jaffe, Richard↗
Thermal Decomposition of Fullerene Mix
Experiments to determine the cause of fullerene decomposition at temperatures above 973k were conducted by spectroscopic analysis of samples heated in vacuo.
decay curves↗
Are Fullerenes Relevant to Cosmochemistry? A New Finding
The abundances of noble gases found in primitive, carbonaceous meteorites are unexpected when compared with our Sun. Known as Q-gases (Q for some unknown carrier dubbed quintessence ), this anomaly has remained a mystery since it was discovered in 1975. Q-gases are characterized by increasing depletions with decreasing atomic number (Z) relative to solar noble gases and normalized to 132Xe (Figure 1). This Q-gas mass fractionation is unexplained, and its investigation is important to understanding the origin of the solar system. However, the subject is fraught with controversy, in part due to the complex nature of Q and in part due to claims of some researchers that cannot be reproduced by other investigators. The topic is discussed in numerous places [e.g., 1-4], with models of Q falling into two basic categories, both involving carbon entrapment of noble gases. First (Group A), there is the conservative two-dimensional view that Q-gases are adsorbed or sorbed onto a "labyrinth" of graphite or carbon grains [5-9], or they undergo active capture onto growing surfaces [6]. Second (Group B), there is the view holding to the remarkable property of carbon discovered in 1985. Carbon can curl up into closed geometries of hexagon- and pentagon-shaped carbon-ring configurations, a property ignored completely by Group A. Group B thinks of Q as a three-dimensional structure of endohedral carbon cages like fullerenes, carbon onions, or some class of carbon nanotubes [3, 4, 10]. Group B does not exclude Group A effects.
Wilson, T. L.↗
Design and Testing of a Fullerene RF Ion Engine
Because of the large mass, low first ionization potential and large electron impact ionization cross-
Fullerene↗
Titan's ionospheric chemistry, fullerenes, oxygen, galactic cosmic rays and the formation of exobiological molecules on and within its surfaces and lakes
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Edward C. Sittler↗
Atomic force microscope studies of fullerene films - Highly stable C60 fcc (311) free surfaces
Atomic force microscopy and X-ray diffractometry were used to study 1500 A-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrte. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.
Snyder, Eric J.↗
Geochemistry and cosmochemistry of fullerenes 3: Reaction of C60 and C70 with ozone
C60 and C70 dissolved in toluene were treated with O2 gas containing 2.6 volume percent ozone and with O3-free oxygen. No reaction products were detected for 0.1 mole of O2 passed through the solution, but destruction of C60 was clearly detectable for a dose of 10(exp -6) moles of O3. C70 was destroyed more slowly than C60. Among the substances remaining in solution, we identified C60O, C70O, C60O2, C60O3, and C60O4. C60 crystals exposed to O3 at room temperature became less soluble in toluene in a matter of days, but oxides were apparently not formed.
Heymann, D.↗
Molecular Static Third-Order Polarizabilities of Carbon-Cage Fullerene and Their Correlation with Three Geometric Properties: Symmetry, Aromaticity, and Size
The static third-order polarizabilities (gamma) of C60, C70, five isomers of C78 and two isomers of C84 were analyzed in terms of three properties, from a geometric point of view: symmetry, aromaticity and size. The polarizability values were based on the finite field approximation using a semiempirical Hamiltonian (AM1) and applied to molecular structures obtained from density functional theory calculations. Symmetry was characterized by the molecular group order. The selection of 6-member rings as aromatic was determined from an analysis of bond lengths. Maximum interatomic distance and surface area were the parameters considered with respect to size. Based on triple linear regression analysis, it was found that the static linear polarizability (alpha) and gamma in these molecules respond differently to geometrical properties: alpha depends almost exclusively on surface area while gamma is affected by a combination of number of aromatic rings, length and group order, in decreasing importance. In the case of alpha, valence electron contributions provide the same information as all-electron estimates. For gamma, the best correlation coefficients are obtained when all-electron estimates are used and when the dependent parameter is ln(gamma) instead of gamma.
Moore, C. E.↗
Curvature Dependent Reactivity of Fullerenes and Nanotubes
Dependence of pyramidalization angle, examples of nanotube surfaces, internal and external reactivity, and binding energies are some of the topics discussed in this conference presentation preprint. Final conclusions include the relationship between the pyramidal angle of the surface and its associated external reaction energy.
Park, Seongjun↗
Computational Nanotechnology of Molecular Materials, Electronics, and Actuators with Carbon Nanotubes and Fullerenes
The role of computational nanotechnology in developing next generation of multifunctional materials, molecular scale electronic and computing devices, sensors, actuators, and machines is described through a brief review of enabling computational techniques and few recent examples derived from computer simulations of carbon nanotube based molecular nanotechnology.
Srivastava, Deepak↗
Fullerene Derived Molecular Electronic Devices
The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal grapheme sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme.
Menon, Madhu↗
Nanotube Heterojunctions and Endo-Fullerenes for Nanoelectronics
Topics discussed include: (1) Light-Weight Multi-Functional Materials: Nanomechanics; Nanotubes and Composites; Thermal/Chemical/Electrical Characterization; (2) Biomimetic/Revolutionary Concepts: Evolutionary Computing and Sensing; Self-Heating Materials; (3) Central Computing System: Molecular Electronics; Materials for Quantum Bits; and (4) Molecular Machines.
Srivastava, Deepak↗