Diamond topology

Fig. 4.27 Restoring force of two different diamond topology interpenetrating networks, with and without random knots, as indicated for Ns 12. (From Ref. 13).

Fd-3m, space group 227, one of the highest symmetry space group patterns. There are, in fact, innumerable possible polytypic patterns within the diamond topology, several of these have been discussed recently by Wen et al. [17] in some detail, and all of them collectively possess the same Wells point symbol of 6, and the corresponding Schlafli symbol of (6, 4). It is only by their symmetry character, that the members of the diamond polytypic series can be distinguished from each other. Thus, the simplest cubic diamond polytype, known as 3C, is shown in Fig. 5. 

To achieve non-zero 7ta—7tb conjugation, the pi NBOs of 18 may polarize in opposite directions, leading to a wavefunction of lower symmetry than the nuclear framework. Alternatively, the nuclear framework may distort to diamond-like D2h geometry. However, each such distortion destabilizes what is already a highly unfavorable Lewis-structure wavefunction, so cyclobutadiene is expected to remain highly destabilized relative to other possible polyene topologies. 

Some general points about interpenetrating networks can be illustrated by the example of Zn(CN)2, which was structurally characterized over half a century ago [3]. It consists of two independent diamond-like nets with the 66-a topology, in which zinc provides the tetrahedral nodes and cyanide provides linear connections between nodes. These two equivalent but independent nets interpenetrate as shown in Figure 4, such that the nodes of one net are located at the centers of the... 

Zn(n) [MT2]3(H20) 3-D super-diamond-like topological network Cubic Fdim 2.163-2.166 ... 

Fig. 6. Snapshot depicting the diamond lattice topology of the polyelectrolyte network. The nodes are shown as oversized spheres, connected by the polymer chains. The counterions are floating freely between the polymers...

Owing to the compressed topology of the reconstructed diamond surface the lattice mismatch is thought to decrease. The carbon atom chains 1 and 2 of carbyne coincide rather closely with the atom positions A of the top layer... 

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