Octakaidecahedron

The compound is a clathrate hydrate, and the most notable feature of the water framework is a novel polyhedral cage, the 18-hedron (octakaidecahedron),[…]

The most interesting feature here is the appearance of a new type of polyhedral cage, the 18-hedron or octakaidecahedron (see Fig. 115).

The d-functions adapted to spherical symmetry divide the sphere in six quadrangles (around the three Cartesian axes) reserved for the e_g sub-shell and twelve hexagons for the t_(2g) sub-shell very similar to a cubic octakaidecahedron projected out to the sphere.

This is a packing of cubes and octakaidecahedra in which there are two types of grain comer geometry.

The rhombic faces of one-third of the rhombicdodecahedra move outwards, resulting in octakaidecahedra (8), which are equivalent to, but larger than, those of figure 2.6(b).[…]If the square faces of the octakaidecahedra continue to grow, thereby shrinking the rhombohexagonal dodecahedra, a simple cubic unimodular structure survives as shown in figure 2.6(e).

It is an octakaidecahedron consisting of a pair of (004) square faces[…]

[…]so that the two can be regarded as single face, with the periphery more accurately described as a polyhedron with 12 vertices and 18 faces, an octakaidecahedron[…]

In the present case, it is an octakaidecahedron with 12 vertices and 18 faces.[…]formed by the oxygen atoms of the peripheral octakaidecahedron,[…]