K- hexagonal

Fig. 2. CO conversions at 363 K in the dry condition (open points) and 353 K in the wet condition (filled points) over lOOmg and 50 mg of Aa/CeOi catal) containing 0.95 wt% Au prepared at different calcination temperatures (373 K (circle), 473 K(square), 573 K(triangle up), 673 K (triangle down), 773 K (diamond), 873 K (hexagon)). The reactants of 100 ml/min, 1 vol% CO and 1 vol% O2 in He, were fed to the catalyst.

A summary of physical and chemical constants for beryUium is compUed ia Table 1 (3—7). One of the more important characteristics of beryUium is its pronounced anisotropy resulting from the close-packed hexagonal crystal stmcture. This factor must be considered for any property that is known or suspected to be stmcture sensitive. As an example, the thermal expansion coefficient at 273 K of siagle-crystal beryUium was measured (8) as 10.6 x 10 paraUel to the i -axis and 7.7 x 10 paraUel to the i -axis. The actual expansion of polycrystalline metal then becomes a function of the degree of preferred orientation present and the direction of measurement ia wrought beryUium. 

In this process, diamond forms from graphite without a catalyst. The refractory nature of carbon demands a fairly high temperature (2500—3000 K) for sufficient atomic mobiUty for the transformation, and the high temperature in turn demands a high pressure (above 12 GPa 120 kbar) for diamond stabihty. The combination of high temperature and pressure may be achieved statically or dynamically. During the course of experimentation on this process a new form of diamond with a hexagonal (wurtzitic) stmcture was discovered (25). 

Solid carbon monoxide exists in one of two aUotropes, a body-centered cubic or a hexagonal stmcture. The body-centered stmcture converts into the hexagonal stmcture at 62 K with a heat of transition of 0.632 kj/mol (0.151 kcal/mol) (5). The melting point at atmospheric pressure is 68.1 K and... 

Fig. 6. Self-consistent band structure (48 valence and 5 conduction bands) for the hexagonal II arrangement of nanotubes, calculated along different high-symmetry directions in the Brillouin zone. The Fermi level is positioned at the degeneracy point appearing between K-H, indicating metallic behavior for this tubule array[17. ...

Fig. 3. (a) Depiction of central Brillouin zone and allowed graphene sheet states for a [4,3] nanolube conformation. Note Fermi level for graphene occurs at K points at vertices of hexagonal Brillouin zone, (b) Extended Brillouin zone pie-ture of [4,3] nanotube. Note that top left hexagon is equivalent to bottom right hexagon. 

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