Graphitic electronic properties

Both in work reviewed herein and in theoretical research by other workers[10-30], a consensus has been reached that anomalous properties (compared to graphite and normal graphitic nanotubes) can be obtained with graphitic nanotubes with diameters of the order of a nanometer. In terms of electronic properties, the nanotubes are expected to fall into two major classes on one hand the moderate band gap nanotubes that do not satisfy the Wj — = 3 /w condition in the... 

Although CNTs showed similar EELS pattern in plasmon-loss and core-loss regions to graphite, SWCNT and fine MWCNT with a diameter less than 5 nm had different features. Furthermore, it has been found out that the angular-dependent EELS along the direction normal to the longitudinal axis of CNT shows stronger contribution from Jt electrons than [Pg.38]

The synthesis of molecular carbon structures in the form of C q and other fullerenes stimulated an intense interest in mesoscopic carbon structures. In this respect, the discovery of carbon nanotubes (CNTs) [1] in the deposit of an arc discharge was a major break through. In the early days, many theoretical efforts have focused on the electronic properties of these novel quasi-one-dimensional structures [2-5]. Like graphite, these mesoscopic systems are essentially sp2 bonded. However, the curvature and the cylindrical symmetry cause important modifications compared with planar graphite. 

The physicochemical properties of carbonaceous materials can be altered in a predictable manner by different types of treatments. For example, heat treatment of soft carbons, depending on the temperature, leads to an increase in the crystallite parameters, La and Lc and a decrease in the d(0 0 2) spacing. Besides these physical changes in the carbon material, other properties such as the electrical conductivity and chemical reactivity are changed. A review of the electronic properties of graphite and other types of carbonaceous materials is presented by Spain [3],... 

Although residue compounds are difficult to characterize experimentally, they should constitute only a minor perturbation on the band structure of pure graphite. Efforts to model the electronic properties in the dilute-concentration limit by perturbing the Slonczewski-Weiss-McClure model for graphite have been made (D5). 

In this contribution it is shown that local density functional (LDF) theory accurately predicts structural and electronic properties of metallic systems (such as W and its (001) surface) and covalently bonded systems (such as graphite and the ethylene and fluorine molecules). Furthermore, electron density related quantities such as the spin density compare excellently with experiment as illustrated for the di-phenyl-picryl-hydrazyl (DPPH) radical. Finally, the capabilities of this approach are demonstrated for the bonding of Cu and Ag on a Si(lll) surface as related to their catalytic activities. Thus, LDF theory provides a unified approach to the electronic structures of metals, covalendy bonded molecules, as well as semiconductor surfaces. 

PAH chemistry is of practical as well as theoretical interest. PAHs can be regarded as well defined subunits of graphite, an important industrial material, which is so far not totally understood at the macroscopic level. In this context, it is our aim to delineate the molecular size at which the electronic properties of PAHs converge to those of graphite. Furthermore, alkyl substituted derivatives of hexabenzocoronene (HBC) form discotic mesophases and, therefore, provide opportunities for materials which allow one-dimensional transport processes along their columnar axis [83,84]. Their application for photovoltaics and Xerox processes is also of current interest. 

Walker, Jr P.A. Thrower, Edits, "The Che-mistty and Physics of Carbon , Marcel Decker, Inc, NY 10016(1973) Vol 8, "The Electronic Properties of Graphite and "The Behavior... 

Vol 10 "The Thermal Properties of Graphite ft "Lamellar Reactions in Gtaphitizable Carbons and in Vol 11 "Highly Oriented Pyrolytic Graphite 7) G. Cohn, Edit, Explsft-Pyrots 7(1), 1974 (Lists Vols 8—11 of the above book and suggests (hat the paper on electronic properties in Vol 8 may be of interest in connection with carbon bridge detonators)... 

The electronic properties of SWNTs depend on the direction in which the graphite sheet rolls up. Graphite itself is a 2-D metal, exhibiting metallic conductivity within the... 

These examples notwithstanding, the unusual electronic properties of HOPG, the adsorption common to EPG, and the relative difficulty of handling anisotropic materials have prevented widespread practical applications. Polycrystalline graphite and glassy carbon exploit some of the same principles as HOPG and PG, but are more broadly applicable. 

Fullerene, black and shiny like graphite, is the subject of active current research because of its interesting electronic properties. When allowed to react with rubidium metal, a superconducting material called rubidium fulleride, Rb3C6o, is formed. (We ll discuss superconductors in more detail in Section 21.6.) Carbon nanotubes are being studied for use as fibers in the structural composites used to make golf clubs, bicycle frames, boats, and airplanes. On a mass basis, nanotubes are up to ten times as strong as steel. 

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