Boron, spheroids

One of the aspects that has been of interest is the incorporation of an external atom in the spheroidal cavity. A variety of metal atoms can, in principle, be trapped in this cavity. Some of the studies have claimed that it is possible to push atoms such as lanthanum, iron and helium inside the spheroidal cavity of CgQ and other fullerenes. Substitution of the carbon in CgQ by boron and nitrogen has been attempted. Interestingly, nitrogen not only substitutes for carbon in the cage but also adds on to Cgo and C-iq. 

The structure of [c/oso-B10H10]2, which is shown in Fig. 30, is that of a bicapped Archimedian antiprism30 . The boron framework may be inscribed in a prolate spheroid with semi-axes a = 1.88 and b = c = 1.43 A 130). The bond distances and angles are quite normal for this type of structure. 

Amovilli and March [4] generalized the simple model in March [1] to boron cages using HF calculations. They found that the equilibrium radius of the spheroidal boron cages is proportional to 4n, where n denotes the number of boron atoms in the cluster. The results of Amovilli and March [4] are therefore redrawn in Figure 4.9 to make the above comment quite concrete. 

FIGURE 4.9 Equilibrium radius (in angstroms) of spheroidal boron cages against n, where n is the number of boron atoms. Triangles refer to ab initio computed values. (Redrawn from C. Amovilli and N. H. March, Chem. Phys. Lett. 347,459, 2001.)... 

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