Graphite, atomic structure

The wave function T i oo ( = 11 / = 0, w = 0) corresponds to a spherical electronic distribution around the nucleus and is an example of an s orbital. Solutions of other wave functions may be described in terms of p and d orbitals, atomic radii Half the closest distance of approach of atoms in the structure of the elements. This is easily defined for regular structures, e.g. close-packed metals, but is less easy to define in elements with irregular structures, e.g. As. The values may differ between allo-tropes (e.g. C-C 1 -54 A in diamond and 1 -42 A in planes of graphite). Atomic radii are very different from ionic and covalent radii. 

Natural diamond Natural graphite Synthetic diamond alloyed with iron, 23 248 in amorphous silica, 22 385 antimony impregnated, 3 53 atomic structure of, 22 232 biologically active, 17 803 as a blast furnace refractory,... 

Crystal lattice packing, 12 249-250 Crystal lattice vibrations, 14 236 Crystalline adsorbents, 1 586, 589. See also Molecular sieves Zeolites for gas separation, 1 631 properties and applications, l 588t Crystalline alkali silicates, atomic structure of, 22 454-455 Crystalline cellulose, 5 373-379 Crystalline epoxy resins, 10 373-374 Crystalline flake graphite, 12 793 manufacture and processing of, 12 781-784... 

Y. Gamo, A. Nagashima, M. Wakabayashi, M. Terai, C. Oshima, Atomic structure of monolayer graphite formed on Ni(lll), Surface Science, 374 (1997) 61-64. 

Fig. 1. Atomic structural models of (a) graphite, and (b), carbon black.

The carbon atoms within each layer are arranged in almost the same manner as in graphite. The layers are nearly parallel to each other however, the relative position of these layers is random, so that there is no order as in the c direction of graphite ( turbostratic structure ) [4.3]. X-ray diffraction permits the determination of crystalline regions within the carbon black primary particle. These regions are... 

Traditionally, the principal forms of carbon have (1) diamond, with its tetrahedral arrangement of atoms (2) graphite, whose structure resembles layers of chicken wire and sometimes (3) amorphous, a poorly defined... 

D. Tomanek, S. G. Louie, H. J. Mamin, D. W. Abraham, R. E. Thomson, E. Ganz and J. Carke, Theory and observation of highly asymmetric atomic structure in scanning-tunneling-microscopy images of graphite, Phys. Rev. B 35, 7790 (1987). 

In the case of vitreous carbon, the component Ogv of csv was measured by the technique used for graphite (Donnet et al. 1982) and found to be 32 mJ/m2. This is five times lower than that of the graphite basal plane and may be explained by the low density of vitreous carbon (1.5 x 103 kg/m3) compared to that of graphite (2.26 x 103 kg/m3) (see also Section 8.1). Because the atomic structure of polished surfaces of vitreous carbon is not known, it is not possible to evaluate the percentage of [Pg.170]

Figure 3-8. Atomic structure of porous graphitic carbon. (Reprinted from reference 48, with permission.)...

Canfado LG, Pimenta MA, Neves BRA, Dantas MSS, Jorio A (2004) Influence of the atomic structure on the Raman spectra of graphite edges. Phys Rev Lett 93 247401... 

Fig. 1 Atomic structures of graphites, a) Bernal structure of perfect three-dimensional graphite, b) Warren structure of two-dimensional turbostatic graphite with no layer registration. (Reproduced by kind permission of Thermo-Hypersil-Keystone.)...

Such experiments with large amounts of heavy-metal oxides in carbon arcs should be done with caution. The oxides are readily reduced under conditions of the arc to die neutral metal, and there is no guarantee that all of these metal atoms will end up safely on the inside of carbon cages. In addition to their toxicity. Finely dispersed lanthanum metal atoms on the outside of graphitic carbon structures are highly pyrophoric, as was demonstrated to us quite memorably when we vented the carbon arc apparatus rapidly to air after our First run. We now bleed in a small amount of air while the apparatus is still under vacuum, converting the surface lanthanum into La20j at a slow, controlled rate. 

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