Capped pentagonal antiprisms

The repulsion energy calculations show that the most stable structure is formed by replacing two adjacent atoms at the vertices of an icosahedron by a single atom at the midpoint of that edge. This edge coalesced icosahedron is slightly more stable than the closely related capped pentagonal antiprism formed by removal of one of the vertices formed by an icosahedron ... 

It can be viewed as a Ni10Bi2 icosahedron encapsulating a Ni atom, as well as a Ni,0 pentagonal antiprism, with an eleventh Ni atom placed in its cavity, capped, on opposite sides, by two Bi atoms. 

Figure 14 shows the molecular structure of the trianion [NiioBi2(jU-is-Ni) (C0)i8] . It is constituted by a Ni-centred pentagonal antiprism of Ni atoms, capped, at opposite sides, by two Bi atoms. 

Fig. 8.4. Coordination geometries for seven- and eight-coordination (a) pentagonal bipyramid, (b) capped trigonal prism, (c) capped octahedron, (d) cube, (e) square antiprism and (/) triangulated dodecahedron. Central atom-ligand bonds are shown by full lines dashed lines indicate the edges of the polyhedral figure.

AlCp )i2] (Fig. 9). This cluster is made of a central distorted square antiprism surrounded by an icosidodecahedron, the 12 pentagonal faces of which being capped by an AlCp unit [133]. DFT calculations have established that this cluster... 

Figure 3.17 Nb clusters low-energy isomers, reprinted from [223]. They have been described as two different cappings of the octahedron for Nbg, a bicapped pentagonal bipyramid (left) and a tricapped octahedron (right) for Nb9, and a bicapped antiprism for Nbio...

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