Graphite lattice plane

Fig. 9.8. High-resolution TEM micrograph of fishbone type carbon fibre. Note the graphite lattice planes with distances in between of 0.34 nm [Courtesy J.W. Geus].

Fig. XVII-18. Contours of constant adsorption energy for a krypton atom over the basal plane of graphite. The carbon atoms are at the centers of the dotted triangular regions. The rhombuses show the unit cells for the graphite lattice and for the commensurate adatom lattice. (From Ref. 8. Reprinted with permission from American Chemical Society, copyright 1993.)...

Synthetic graphite flakes, obtained from Timrex Inc., whose morphology has been characterized by a high level of crevices in the facets perpendicular to the basal planes, through which lithium ions are inserted into the graphite lattice (edge planes). 

Our basic example is the graphite lattice sheet, i.e. the 3-valent tiling 6, 3 of the plane by 6-gons. At every vertex of this tiling, we can substitute a 0-elementary (5, 3)-polycycles, either Ei or C3. If we substitute only Ei, we obtain a ( 5, 12, 3)-plane that is 12R0. In order to obtain a ( 5, 13, 3)-plane, we need to substitute a part of the E, by some C3, such that every 6-gon is incident... 

Proof. Such tori can be obtained as quotients of a ( 5, b], 3)-plane. We will get again such a plane from the graphite lattice 6,3 with added structure on it On any vertex of the structure below, which is incident to an boldfaced edge, we put a (5,3>-polycycle D, while on other vertices we put a (5,3)-polycycle E. The obtained ( 5, b, 3)-plane is bR. ... 

Proof. Consider the graphite lattice 6,3 and put a 5-gon in every vertex of it The obtained structure is, clearly, a ( 5,8, 3)-plane, which is 8/ 2- In order to obtain ( 5, b, 3)-planes with b > 8, we need to modify the structure. The 5-gons can be organized into pairs of adjacent ones. Every such pair, which is highlighted in the diagram below, can be changed into a (5,3)-polycycle E2n with n > 1. 

MAGNETIC SUSCEPTIBILITY. Pinnick (58) has correlated the magnetic susceptibility of synthetic graphite with the a-dimension of the lattice plane. There is a sharp increase in susceptibility as a grows from 50 to 150 A., and the susceptibility remains constant thereafter to 1000 A. Juza (39) has shown that the adsorption of oxygen on charcoal at room temperature is molecular, as magnetic susceptibility does not change. 

Cleavage of bulk crystals to expose clean, defined lattice planes is possible for brittle substances. Some materials, like mica or highly oriented pyrolytic graphite (HOPG) that exhibit a layered structure, are readily cleaved by just peeling off some layers or using a razor blade. For other materials the so-called double-wedge technique can be used (Fig. 8.8). 

Elastic neutron diffraction was first performed (analyzer in Fig. 1 set to zero energy transfer) to establish the structure of the monolayer at low temperature. Three Bragg reflections were observed which could be indexed by a triangular lattice having a nearest-neighbor distance about 10% smaller than required for a 3 X /3 R30° commensurate structure (every third carbon hexagon in the graphite basal plane occupied). 

For Raman scattering measurement, a freshly cleaved sample is directly illuminated with the Ar-ion laser, and the resulting spectrum, accumulated during 10 min, is shown in Fig. 23. The band at 1580 cm 1 corresponds to the in-plane C-C breathing mode of the whole graphite lattice, namely the E2g mode. The band at 2730 cm-1 is an overtone of a lower-energy vibration, and... 

The same can be done in the graphite lattice as show in Fig. 2. The bonding force acting between two neighboring atoms can be directly demonstrated as a function of interatomic separation, resulting in anisotropic properties. The bond energy in the c direction is commonly called van der Waals bond or n electron interaction and is estimated to be 17-33 kJ/mol between the planes as compared to 430 kJ/mol of chemical covalent nature or tr-bond within the planes [37]. 

Another adsorbate whose adsorption on the graphite basal plane has been the subject of a number of investigations is benzene [41]. This molecule lies (mostly) flat on the surface at temperatures up to 120 K and forms solid films that are commensurate with the basal plane lattice, but its size is such that the lattice size is ylSx- 5 at temperatures up to 2D melting. However, the melting process for this... 

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