Tetrahedron stacking

Li et al. assumed that the stack of spherical catalyst particles in a packed bed agreed with the above tetrahedron stack model, and ignored the gravity and wall effects. In the measurement of WSCS, each sphere on the top of layer is subject to a downward pressure F under the effect of the pressure P. 

No example is known to us. If we form the double layers with the layers of Figure 18c or d, we obtain units MX2 in which each tetrahedron is now sharing its four vertices with one other tetrahedron. Stacking these perforated sandwiches in AAA sequence would create a funny channel layer structure, e.g. as a hypothetical modification of Si02. There exist silicates such as CaAl2Si20g [34] that do indeed contain these perforated double layers but the large alkaline-earth cations are located between adjacent layers, stuffing the channels. 

The sculpture shows artistically stacked tetrahedra. The molecular geometry for the molecule CCI4 is that of a tetrahedron. 

Goto, T., Tamura, H., and Kondo, T., Chiral stacking of cyanin and pelargonin — soluble and insoluble aggregates as determined by means of circular dichroism. Tetrahedron Lett., 28, 5907, 1987. 

If the layer anions of Figure 19.7d are stacked on top of one another and the terminal O atoms are shared, an infinitely extended three-dimensional structure is obtained in which all four O atoms of each Si04 tetrahedron are shared between two Si atoms, resulting in silica (SiC>2). The mineral quartz is one of many crystalline forms of SiOo. 

Clay minerals are formed by two building blocks [93] tetrahedrons of oxygen with Si4+ ions in their centers or octahedrons of oxygen with Al3+ or Mg2+ in their centers. The tetrahedrons share oxygens and form hexagonal rings. Some oxygen atoms form hydroxyls, in particular when the clay is filled with Ca2+. This pattern can be repeated ad infinitum to form flat tetrahedral sheets. Similarly, the octahedrons are linked to form octahedral layers. The tetrahedral and octahedral sheets can be stacked on top of each other in various forms to build the different kinds of clays. 

Mewshaw RE, Marquis KL, Shi X, McGaughey G, Stack G, Webb MB, Abou-Gharbia M, Wasik T, Scerni R, Spangler T, Brennan JA, Mazandarani H, Coupet J, Andree TH (1998) Tetrahedron 54 7081... 

Hoshino, T, Matsumoto, U., Harada, N., Goto, T. (1981). Chiral excitation coupled stacking of anthocyanins Interpretation of the origin of anomalous CD induced by anthocyanin association. Tetrahedron Lett., 22, 3621-3624. 

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