Cages geometrical structure

The first pairwise contraction leads to the formation of the 3-valent structure of pentagons and hexagons, which is the cage structure of the Ceo fiillerene molecule and, with equal edge lengths, is the geometrical structure known as the truncated icosahedron. 

Dent Glasser et al. found that metal cations can affect the polymeric state of silicate ions, the polymerization rate and form of silicon and aluminum species, and the properties of the gel.[40 41] In addition, it has been confirmed by extensive experimental data that there is a tight correlation between the metal cations and small cage-like structural units of the resultant zeolites (see Table 5.11 for details), i.e., the size of the cations or hydrated cations matches that of these small cages. One type of cation could template different structures under different conditions as well. Studies indicate that metal cations will affect the structure of zeolites via their electropositivity, size, and geometric configuration. 

A commonly discussed topic has been the geometrical structure of carbon species including the doped ones. Do the species have the form such as chains, rings, multirings or three dimensional cage structures like the Ceo molecule. Some answers to these problems have been provided by the groups of Jarrold... 

Clusters with interstitial atoms are an interesting class of polynuclear complexes. Several examples of compounds with interstitial atoms (H, C, Ge, N, P, S, etc.) have been reported. These compounds exhibit special behavior because the presence of main-group atoms in the cluster cage influences the chemical reactivity and stability of the system and its geometric structure. In the following section we consider some of these peculiarities, related both to the stability and to the electronic properties of clusters with interstitial elements. 

Fig. 20.5 a Shell-resolved LDOS of Aujs and AU55 clusters b size-resolved DOS of Aui3 55 i47 solid clusters and Ag12.42.134 hollow cages and c activation energies for CO oxidation pertained to different geometric structures of gold [49]... 

Since the presentation of this model new data have appeared which allow various tests and new conclusions. The diffusion coefficients of Karger (14), together with Equation 1 and the median jump time from the relaxation data at room temperature yield a jump distance of 2.7 A for the zeolitic water as compared with 2.2 A in bulk water (see Table III for a data summary). One might be tempted to explain the jump distance in terms of some geometrical constant of the zeolite structure such as the distance between Sn and Sm ionic sites (40), but with the cages full of... 

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