Irregular dodecahedron

Fig. 26. Dimensions of the irregular bicapped trigonal prism around octacoordinated So(III) in [HSc(trop)4]2. The vertical dotted line indicates the approximate 4 axis to illustrate the distortion of this polyhedron towards a dodecahedron...

Figure 2.5 Three cavities in gas clathrate hydrates (a) pentagonal dodecahedron (512), (b) tetrakaidecahedron (51262), (c) hexakaidecahedron (51264), (d) irregular dodecahedron (435663), and (e) icosahedron (51268).

The Irregular Dodecahedron (435663) and the Icosahedron (51268). Single crystal diffraction data for sizes of structure H cavities (435663 and the 51268 shown in Figures 2.5d,e) have been performed by Udachin and coworkers (Udachin and Lipkowski, 1996 Udachin et al., 1997b Kirchner et al., 2004). The radii of the 435663 and 51268 cavities were determined to be 4.04 and 5.79 A, based on single crystal x-ray diffraction data (Udachin et al., 1997b), as indicated in Table 2.1. 

FIGURE 2.14. Some of the various shapes (hahits) of crystals that can result from a crystal structure with a cubic unit cell, (a) Models of a cube, octahedron, and rhombic dodecahedron, composed of cubic unit cells, (b) Tetrahedron, (c) cube, (d) octahedron, (e) rhombic dodecahedron, (f) tetrahexahedron, (g) icositetrahedron, and (h) irregular dodecahedron (pyritohedron). The corresponding stereographic projections are also shown, with filled circles for the northern hemisphere and open circles for the southern hemisphere (see Figure 2.13). (Models courtesy Amy Kaufman). 

Fig. 10.2, they are pentagonal dodecahedron (5 " ), tetrakaidecahedron (5 6 ), hexakaidecahedron (5 6" ), irregular dodecahedron (4 5 6 ), and icosahedron (5 6 ). The formalism X" is used to describe the structure of each cavity, where X denotes the type of cage face (4—square, 5-pentagon, and 6-hexagon), and n represents the number of such kinds of face in that cavity. The three structures of gas hydrates comprise different cavities 5 and 5 6 cavities form si, 5 and 5 6 cavities form sll, and sH is formed by 5, 4 5 6, and 5 6 cavities. 

Fig. 10.2 Five building polyhedra of gas hydrate structures pentagonal dodecahedron (5 ), tetrakaidecahedron (5 6 ), hexakaidecahedron (5 6 ), irregular dodecahedron (4 5 6 ), and icosahedron (5 6 ) [10], Reprinted by permission from Springer Science and Business Media...

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