Cubic close-packing, ccp

The metal nuclei of the so-called full-shell clusters, also referred to as magic number clusters, generally exhibit hexagonal or cubic close packing (ccp). Figure 6 shows the stepwise formation of the first magic-number clusters built by 13, 55, 147, and 309 atoms. 

Cubed compound, in PVC siding manufacture, 25 685 Cube lattice, 8 114t Cubic boron nitride, 1 8 4 654 grinding wheels, 1 21 hardness in various scales, l 3t physical properties of, 4 653t Cubic close-packed (CCP) structure, of spinel ferrites, 11 60 Cubic ferrites, 11 55-57 Cubic geometry, for metal coordination numbers, 7 574, 575t. See also Cubic structure Cubic symmetry Cubic silsesquioxanes (CSS), 13 539 Cubic structure, of ferroelectric crystals, 11 94-95, 96 Cubic symmetry, 8 114t Cubitron sol-gel abrasives, 1 7 Cucurbituril inclusion compounds,... 

The orange coloured lepidocrocite, y-FeOOH, is named after its platy crystal shape (lepidos scale) and its orange colour (krokus = saffron). It occurs in rocks, soils, biota and rust and is often an oxidation product of Fe ". It has the boehmite (y-AlOOH) structure which is based on cubic close packing (ccp) of anions. 

Most of the metallic elements of the Periodic Table crystallize in one or more of the highly symmetric structure types A1 (cubic close packed, ccp ), A2 (body-centered cubic, bcc) and A3 (hexagonal close packed, hcp) ... 

Polyhedra in Cubic Close-Packed (ccp) and Hexagonal Close-Packed (hep) Structures... 

The relationship between cubic close-packed (ccp) structures and ionic compounds of type B1 is obvious. Interstitial sites with respect to metal positions are at fractional coordinates of the type 00 and equivalent to the ionic sites in Bl. The Madelung constant of Al type metals with interstitially localized free electrons is therefore the same as that of rocksalt structures. It is noted that the interstitial sites define the same face-centred lattice as the metal ions. 

The NaCl-type structure of MgO is characterized by an FCC cubic close-packed (CCP) anionic framework of O2, with all the octahedral positions filled with Mg2+. In the CCP structure, there are four octahedral sites per unit cell and eight tetrahedral sites (see Figures 1.6 and 1.7). 

Coordination Number It is the number of atoms or spheres that surround a single atom or sphere in a crystal. The coordination number (C.N.) of both hep and cubic close packing (ccp) stmeture is 12. In bcc coordination number is 8 and in fee the coordination number is 6. 

The monometallic carbides and nitrides often adopt simple crystal structures (Fig. 1 ) with the metal atoms arranged in cubic close-packed (ccp), hexagonal close-packed (hep) or simple hexagonal (hex) arrays. The nonmetallic elements, C, N, and O, occupy interstitial spaces between metal atoms, and for this reason the materials are also known as interstitial alloys. 

Consider a pure metal with the cubic-closed packed (CCP) structure (space group Fm 3 m). In this structure, there is an atom at each corner of a cube and an atom at the center of each of the cube s six faces. How many atoms are there in the unit cell Which point could be chosen as the origin What are the point-coordinates of all the atoms, relative to the origin Is the origin on a special position What is the multiplicity of the origin ... 

Figure 2.9. Representation of (a) simple cubic packing and (b, c) close-packing. The two sites that may be occupied by subsequent layers in close-packing, B and C sites, are shown. This results in two types of packing ABABAB... (hexagonal close-packing, hep), and ABCABC... (cubic close-packing, ccp).

The similar organization energies of the hep and ccp lattices make their intergrowth easy in mesoporous materials synthesized from both simple surfactant and copolymer surfactant. Intergrowth with cubic close-packed (ccp) structure was typically observed... 

The Sodium Chloride Crystal Structure. Each atom has six nearest neighbors, with octahedral geometry. This arrangement is known as cubic close packed (ccp). 

Spinel and inverse spinel structures are based on cubic close-packed (ccp) arrangements of ions. Draw a representation of a unit cell of a ccp arrangement of ions. How many octahedral and tetrahedral holes are there in this unit cell ... 

Fig. 2-10. The occurrence of hexagonal close-packed hep), cubic close-packed ccp) and body-centered bcc) structures among the elements. Where two or more symbols are used, the largest represents the stable form at 25 °C. The symbol labelled hep ccp signifies a mixed. .. ABCABABCAB. .. type uf ciuSc packing, with overall hexagon a 1 symmetry. [Adapted, with permission, from H. Krebs, Grundzuge der anorganisken Kristallchemie,...

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