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An organic material composed of neutral free radicals based on the spirobiphenalenyl system exhibits a room temperature conductivity of 0.3 siemens per centimeter and a high-symmetry crystal structure. It displays the temperature-independent Pauli pararnagnetism characteristic of a metal with a magnetic susceptibility that implies a density of states at the Fermi level of 15.5 states per electron volt per mole. Extended Huckel calculations indicate that the solid is a three-dimensional organic metal with a band width of ~0.5 electron volts. However, the compound shows activated conductivity (activation energy, 0.054 electron volts) and an optical energy gap of 0.34 electron volts. We argue that these apparently contradictory properties are best resolved in terms of the resonating valence-bond ground state originally suggested by Pauling, but with the modifications introduced by Anderson., The familiar properties of inorganic metals, such as the inverse temperature dependence of their conductivity, are well understood in terms of band theory, in which valence electrons populate delocalized states [...]

The nature of single-walled carbon nanotube (SWNT) -solvent interaction, which is responsible for the stabilization of ultrasonicated dispersions, is investigated by various techniques. The degradation of SWNTs was observed under conditions that might be expected to remove covalent functionalities, and the chemical interaction of the sonopolymer with the SWNTs was found to be irreversible.

The diamagnetic and paramagnetic ring currents present in the carbon allotropes, such as fullerenes and C60, considerably affect the magnetism of these molecules. In C60, the sigma-bond anisotropy causes the endohedral chemical shift. The ring currents are responsible for the chemical shift of the surface protons in C60. The study of magnetism shows the presence of pie-electrons moving in three dimensions.

Previous high-resolution electron microscopy (HREM) observations of the carbon nanotubes have led to a 'Russian doll' structural model that is based on hollow concentric cylinders capped at both ends. The structures of the carbon nanotubes and particles were characterized here by bulk physical and chemical property measurements. The individual nanostructure is as compressible as graphite in the c axis, and such nanostructures can be intercalated with potassium and rubidium, leading to a saturation composition of '[MC.sub.8]' These results are counter to expectations that are based on a Russian doll structure. HREM after intercalation with potassium and deintercalation indicates that individual nanoparticles are a 'paper-mache' of smaller graphite layers. Direct current magnetization and electron spin resonance measurements indicate that the electronic properties of the nanostructures are distinctly different from those of graphite. Although the nanostructures have distinct morphologies and electronic properties, they are highly defective and have a local structure similar to turbostratic graphite., Modification of the spark erosion technique (1, 2) for the synthesis of fullerenes has led to the discovery (3) and preparation of macroscopic quantities of carbon nanotubes (4). HREM images [...]

Van der Waals forces that bind [C.sub.60] molecular solids are found to be sufficient strong to allow the reproducible fabrication of free-standing [C.sub.60] membranes on (100) silicon wafers. Membranes, 2000 to 6000 angstroms thick, were fabricated by a modified silicon micro-machining process and were found to be smooth, flat, and mechanically robust. An important aspect of the silicon-compatible fabrication procedure is the demonstration that [C.sub.60] films can be uniformly and nondestructively thinned in a C[F.sub.4] plasma. Young's modulus and fracture strength measurements were made on membranes with areas larger than 6 millimeters by 7 millimeters. It may be possible to use [C.sub.60] membranes for physical property measurements and applications., The description of a simple technique to produce macroscopic amounts of [C.sub.60] molecules (1) has stimulated numerous investigations into how these molecules can be assembled into solid forms. Crystals (1-3) [...]

The dielectric constant [Epsilon] and conductivity Σ of undoped [C.sub.60] single crystals have been measured as a function of temperature, 10 K < T < 330 K, and frequency, 0.2 kilohertz < f < 100 kilohertz. On cooling below the first-order structural phase transition at 260 K, a Debye-like relaxational contribution to the dielectric response is observed, which requires the presence of permanent electric dipoles. The relaxation rate is thermally activated with a broad distribution of energies centered at 270 millielectron volts. The existence of a dipole moment in [C.sub.60] is unexpected, because it is precluded by symmetry for the pure ordered cubic phase. These data suggest that the high degree of frozen-in orientation disorder of the [C.sub.60] molecules for the existence of electric dipolar activity., The discovery and synthesis of the icosahedral carbon molecule [C.sub.60] [1] and its subsequent crystallization [2] have stimulated great gravity directed toward understanding the static and dynamic properties of its [...]

A new organic molecular conductor, based on a spiro-biphenalenyl neutral radical, simultaneously exhibits bistability in three physical channels: electrical, optical, and magnetic, in the paramagnetic state, the unpaired electrons are located in the exterior phenalenyl units of the dimer, whereas in the diamagnetic state the electrons migrate to the interior phenalenyl units and spin pair as a π-dimer. Against all expectations, the conductivity increases by two orders of magnitude in the diamagnetic state, and the band gap decreases. This type of multifunctional material has the potential to be used as the basis for new types of electronic devices, where multiple physical channels are used for writing, reading, and transferring information., The processing of information is based on the ability to control and retrieve changes in a particular physical property of a material, such as the electrical, magnetic, or optical response. [...]

Organic field-effect transistors have been developed that function as either n-channel or p-channel devices, depending on the gate bias. The two active materials are a-hexathienylene (α-6T) and [C.sub.60] The characteristics of these devices depend mainly on the molecular orbital energy levels and transport properties of α-6T and [C.sub.60] The observed effects are not unique to the two materials chosen and can be quite universal provided certain conditions are met. The device can be used as a building block to form low-cost, low-power complementary integrated circuits., Organic transistors have characteristics that make them attractive in applications such as large-area electronics, including low-cost deposition processes, compatibility with plastic substrates, and steadily improving performance. Thin-film transistors (TFFs) with [...]

Elemental carbon can be synthesized in a variety of geometrical forms, from three-dimensional extended structures (diamond) to finite molecules ([C.sub.60] fullerite). Results are presented here on the magnetic susceptibility of [...]

The fullerene [C.sub.60] can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine [C.sub.60] on reheating to 300°C at ambient pressure. For synthesis temperatures between 300° and 400°C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a, = 13.6 angstroms. When treated at 500°to 800°C at the same pressure, [C.sub.60] transforms into a rhombohedral structure with hexagonal lattice parameters of [a.sub.o] = 9.22 angstroms and co = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the [C.sub.60] molecules are linked., Although [C.sub.60] molecules are extremely stable at ambient conditions, nonhydrostatic compression induces a transformation of [C.sub.60] to diamond (1) or unknown structures above 15 GPa (2-4). Light irradiation is also [...]

A new molecular conductor relies on hole doped and electron doped charge transfer for carrier creation. The conductor has energy bands which are created from single-dimensional stacks of neutral pi-radicals. This enables conduction by the transfer of electrons from the conduction band which precedes the doping by an acceptor. The new conductor has a molecular formula of 1,4-phenylene-bis(dithiadiazolyl) diradical 1, 4-((S2N2C)C6H4(CN2S2)).

The alkali-metal fulleride Na2CsC60 is a f.c.c. superconductor with and a value of 14.132 angstroms and a transition temperature (Tc) of 10.5 K. Since cations can occupy the octahedral site of the fulleride, attempts were made to introduce molecular ammonia (NH3) to Na2CsC60. Ammonia was introduced by exposing the sample to 380 torr of NH3 gas distilled from a sodium/liquid-ammonia solution through a vacuum manifold. Introduction of the ion resulted in an increase in a to 14.473 angstroms and an increase in Tc to 29.6K.

Superconductivity has previously been discovered for compounds in which an alkali metal is intercalated with the C(sub 60) fulleride molecule. All such materials have had face-centered cubic crystal structure, but a body-centered cubic phase may be formed by intercalating fulleride with barium. This molecule is also superconducting, and has a ratio of six barium atoms to one fulleride. This ratio gives a different external coordination number for the fulleride than previous superconductors, suggesting that some intrinsic property of the fulleride is responsible for the superconductive mechanism.

The temperature- and concentration-dependent resistivities of annealed [Ca.sub.x][C.sub.60] and [Sr.sub.x][C.sub.60] films were measured near room temperature. Resistivity minima were observed at x = 2 and 5. The resistivities of these films were [rho.sub.min] 1 ohm-centimeter for x = 2 and [rho.sub.min] [10.sup.-2] ohm-centimeter for x = 5. This latter value is comparable to the resistivities found in similar experiments on [K.sub.3][C.sub.60] films. There is a maximum in the resistivity between x = 2 and 3, and another at x 7. The conductivity is activated over the whole range of compositions, and the activation energy scales with the logarithm of the resistivity. The results suggest that the conductivity and superconductivity observed in [Ca.sub.5][C.sub.60] are associated with the population of bands derived from the [t.sub.1g] level of [C.sub.60]., Solid [C.sub.60] and [C.sub.70] undergo doping with alkali metals to produce conductors[1]. For A = K or Rb, the [A.sub.3][C.sub.60] phases are superconductors[2-5]. It has been shown that Ca intercalates [...]

The room temperature Raman spectra of the intramolecular modes between 100 [cm.sup.-1] and 2000 [cm.sup.-1] are reported for alkali-metal doped [A.sub.x.C.sub.60] films. For A + K, Rb, and Cs, phase separation is observed with the spectra of [C.sub.60], [K.sub.3.C.sub.60], [K.sub.6.C.sub.60], [Rb.sub.3.C.sub.60], [Rb.sub.6.C.sub.60], and [Cs.sub.6.C.sub.60] phases reported. The x = 3 phases show only three Raman active modes: two of [A.sub.g] symmetry and only the lowest frequency [H.sub.g] mode. The other [H.sub.g] modes regain intensity in the x = 6 films, with several mode splittings observed. For A = Na, such phase separation is not clearly observed, and reduced mode shifts are interpreted as due to incomplete charge transfer in these films., CONDUCTING [1] AND SUPERCONDUCTING [2] compounds of [A.sub.x.C.sub.60] (0 [is less than or =] x [is less than or =] 6) have recently been prepared by intercalating alkali metals (A) [...]

THE DISCOVERY OF NEW METHODS of synthesis of fullerene carbon molecules [1] has led to a proliferation of studies of the properties of solid [C.sub.60] [2-6]. Most of these studies [...]

A novel approach toward development of advanced chemical sensors based on chemically functionalized single-walled carbon nanotubes (SWNTs) is demonstrated. P2-SWNTs exposed to 100 ppm NH3 exhibit a behavior, which is typical of pristine SWNTs.

The influence of Ni-Y catalyst composition on the bulk scale synthesis of a single-walled nanotubes (SWNTs) is studied using solution phase near-infrared spectroscopy. A range of catalyst compositions is invariant to the scale of the EA synthetic procedure, and this suggests that it will be possible to significantly reduce the cost of production and to further improve the quality of bulk quantities of SWNTs that are suitable for large-scale applications.

A solution-phase near-IR (NIR) spectroscopic study of a range of carbon materials with an emphasis single-walled carbon nanotubes (SWNTs). The applicability of Beer's law for all of the carbon materials included in here within a range of concentrations in dimethylformamide (DMF) is demonstrated.

The Extended Huckel Theory (EHT) calculations of the band electronic structure of substituted pentacene derivatives and the polymorphs of the parent compound are presented. An analysis on these calculations reveals that there are wide disparities among the bandwidth and electronic dimensionalities of these compounds.

The synthesis, crystallization and solid-state properties of radical crystallized compound, and the conducting pathways of these solids are presented. The viability of conducting pathways in organic molecular solids is discussed.

Theoretical support for the proposition made by Liu and colleagues that carbon toroids show interesting transport properties, is provided. The calculated structure of the C576 toroid was used as a test case, using the finite-field London theory to measure magnetic properties. The magnetic properties were related to the electrical conductivity by scaling the quantum mechanical result with the free-electron value of magnetic susceptibility.

A new formulation of the current within the London approximation allows the calculation of ring currents in topologically complex molecules. Application of this theory to [C.sub.60] demonstrates the existence of remarkable π electron ring currents. Paramagnetic currents, in size comparable to the ones in benzene, flow within the pentagons, whereas weaker diamagnetic currents flow all around the [C.sub.60] molecule. The overall vanishing ring-current magnetic susceptibility results from a cancellation of diamagnetic and paramagnetic contributions. The presence of ring currents significantly affects chemical shifts as measured in nuclear magnetic resonance experiments. In contrast to the magnetic susceptibility, which is a property of the molecule as a whole, chemical shifts are sensitive to the local magnetic field and the effect of ring currents does not vanish., The initial suggestion by Kroto and co-workers [1] that the sea of π electrons on the inner and outer surface of [C.sub.60] could give rise to remarkable ring currents has [...]

The pseudo--one-dimensional (psuedo-1D) conjugated electronic structure of single-walled carbon nanotubes (SWNTs) allows them to exhibit semiconducting and metallic properties and to exhibit ballistic transport (1). We show that their unique [...]

Reports on the room temperature Raman spectra of certain intramolecular modes for alkali-metal doped AxC60 films. Phase separation of A; Phases of `x' = 3; Intensity of `Hg' modes; Observation of mode splittings; Results of A = Na observations.

Presents research which constructed and used a silicon micromechanical magnetometer. Use in 60-tesla pulsed magnetic fields; Features of device; Device's response and sensitivity; Observations of quantum oscillations in device.