Non close packing

In the f.c.c. and c.p.h. crystal structures, each atom has 12 nearest neighbours and is therefore SJiid to have a co-ordination number oi 12. In the non-closed-packed b.c.c. structure, on the other hand the co-ordination number is only 8. In the f.c.c. structure the four octahedral 111 ) planes are close... 

In any crystal structure, the close-packed or closest-packed planes are the lowest energy planes. On all other planes, the density of atoms is lower, and the interatomic distance and the energy of the plane are greater. Contrary to intuitive expectations, the diameter of the largest holes or interstices between atoms in the close-packed f.c.c. structure is considerably greater than the diameter of the largest interstices between atoms in the non-close-packed b.c.c. structure. 

Hoogenboom JP, Retif C, de Bres E, de Boer MV, van Langen-Suurling AK, Romijn J, van Blaaderen A (2004) Template-induced growth of close-packed and non-close-packed colloidal crystals during solvent evaporation. Nano Lett 4 205-208... 

The chemisorption of water on ZnO has been investigated by Nagao and Morimoto (147). Dent and Kokes (148) explained H2 chemisorption and ethylene hydrogenation on the basis of a model in which the (0001), (0001), and non-close-packed faces such as (1010) planes of the wurtzite crystal structure are assumed to form the external crystal surface. Chemisorption of H2 was suggested to occur on Zn—O pair sites, since the Zn—H and O—H stretching... 

Non-close-packed structure (in register, corresponding to A A layers)... 

Non-close-packing simple cubic and body-centred cubic arrays... 

Cinchonidine in its lowest energy state is L-shaped and it can approach a Pt (100) or Pt (111) surface in a configuration that would permit adsorption by the quinoline moiety without conformational disturbance (22]. The model proposed by Wells involves the flat adsorption on the platinum surface in a non-close packed array, thus leaving exposed shaped ensembles of platinum atoms. 

This results in very non-closed packed CO-polyhedra and previous ideas about CO ffuxionality for smaller clusters are certainly not sustainable for these higher nuclearity clusters. 

Modification of the surfaces of coUoidal silica spheres with silane coupling agents enables transfer of the particles to nonpolar solvents. With 3-methacryloxypropyltri-methoxysilane bonded to the surface, the particles have been transferred from water to the polymerizable monomer, methyl acrylate. Electrostatic repulsion due to a low level of residual charge on the particle surfaces cause the dilute dispersions of particles to form a non-close packed colloidal crystalline array (CCA). Polymerization of the methyl acrylate with 200 nm diameter silica spheres in a CC fixes the positions of the spheres in a plastic film by the reactions shown in Figure 11.14. The difriaction... 

Figure 12.3 The green overhang of linker A is self-complementary therefore, DNA-AuNPs hybridized to linker A are self-complementary and behave as a single component system. Maximizing the number of particle-particle interactions results in a close-packed structure depicted by an FCC unit cell Hie red and blue oveihang of linker X and linker Y are complementary and DNA-AuNPs hybridized to linkers X and Y are complementary and behave as a binary system. Maximizing the number of particle-particle interactions results in a non-close-packed structure depicted by a BCC unit cell.

In general, the atomic geometry of their surfaces is close (within 5%) to that of the bulk solid, except that contractions of the upper, larger spacing appear possible for the non-close-packed faces... 

The CCA, however, can be prepared as macroscopically ordered arrays of non-close-packed spheres. This self assembly is the result of electrostatic repulsions between colloidal particles, each of which has numerous charged surface functional groups. We have concentrated on the development of CCA which diffract light in the visible spectral region, and have generally utilized colloidal particles of ca. 100 nm diameter (7). These particles have thousands of charges which result from... 

The adsorbate-adsorbate interactions may be repulsive they always are repulsive at sufficiently small adsorbate-adsorbate separations. At larger separations they may be attractive, giving rise to the possibility of island formation. They may also be oscillatory, moving back and forth between attractive and repulsive as a function of adsorbate-adsorbate separation, with a period of several angstroms giving rise, for example, to non-close-packed islands. 

When the cations get somewhat larger they force the anions apart, and we get non-close-packed stmcture types like the fluorite and its derivatives (pyrochlore, rare-earth oxide stmctures, etc.)... 

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