Lattices of diamonds

In the crystal lattice of diamond, each atom of carbon is surrounded tetrahedrally by four other atoms to which the central atom is bound by four (7 bonds. Each crystal is thus a large single molecule in which every atom is joined to four others by homopolar bonds. The bond between the carbon atoms is almost identical in properties with that of the single C—G bond in hydrocarbons, thus the interatomic distance in diamond is i 54 A and the value of the dielectric constant, 5 3, leads to a value for the polarizability of the bond of i cc, which is only slightly less than the value for the G—G bond in hydrocarbons. 

In the lattice of diamond, there are four equal covalent bonds located so that they form an angle of 109° 28 to each other (Figure 4.4) each one is formed by a pair of electrons with oppositely directed spins. In diamond lattice (formed by the carbon atoms) the four nearest-neighbor bonds form the vertices of a regular tetrahedron. 

Diamond-like carbon (DLC) films are hard, amorphous films with a significant fraction of sp -hybridized carbon atoms and which can contain a significant amount of hydrogen. Depending on the deposition conditions, these films can be fully amorphous or contain diamond crystallites. These materials are not called diamond unless a full three-dimensional crystalline lattice of diamond is proven. 

Figure 29.1 Crystal structures of ZnS. (a) Zinc blende, consisting of two, interpenetrating, cep lattices of Zn and S atoms displaced with respect to each other so that the atoms of each achieve 4-coordination (Zn-S = 235 pm) by occupying tetrahedral sites of the other lattice. The face-centred cube, characteristic of the cep lattice, can be seen — in this case composed of S atoms, but an extended diagram would reveal the same arrangement of Zn atoms. Note that if all the atoms of this structure were C, the structure would be that of diamond (p. 275). (b) Wurtzite. As with zinc blende, tetrahedral coordination of both Zn and S is achieved (Zn-S = 236 pm) but this time the interpenetrating lattices are hexagonal, rather than cubic, close-packed.

Graphite is another solid form of carbon. In contrast to the three-dimensional lattice structure of diamond, graphite has a layered structure. Each layer is strongly bound together but only weak forces exist between adjacent layers. These weak forces make the graphite crystal easy to cleave, and explain its softness and lubricating qualities. 

Because there are no sarcomeres in smooth muscle, there are no Z lines. Instead, the actin filaments are attached to dense bodies. These structures, which contain the same protein as Z lines, are positioned throughout the cytoplasm of the smooth muscle cell as well as attached to the internal surface of the plasma membrane. Myosin filaments are associated with the actin filaments, forming contractile bundles oriented in a diagonal manner. This arrangement forms a diamond-shaped lattice of contractile elements throughout the cytoplasm. Consequently, the interaction of actin and myosin during contraction causes the cell to become shorter and wider. 

Carbon nanotubes (CNTs) constitute a nanostructured carbon material that consists of rolled up layers of sp2 hybridized carbon atoms forming a honeycomb lattice. After diamond, graphite and fullerenes, the one-dimensional tubular structure of CNTs is considered the 4th allotrope of carbon (graphene is the 5th). 

Figure 5. Stereographc representation of the number of accessible lattice orientations for atomic resolution analysis of diamond at different resolution limits." ...

Aggarwal K. G. (1967). Lattice dynamics of diamond. Proc. Phys. Soc, 91 381-389. 

Why is graphite agooil conductor wnereas diamond is not (Both contain infinite lattices of covalently bound carbon atoms.)... 

Diamond, the hardest of natural materials, consists of a lattice of carbon atoms arranged in a tetrahedral slruclure at equal distances apait (1.544 A) and bonded by electron pairs in localized molecular orbitals formed by overlapping of Ihe. /> hybrids. See aiticle on Diamond. 

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