Condensed cluster chains

Figure 22 Structure of a condensed cluster chain in Gd2Cl3...

There are several interesting families of inorganic mixed-valence compounds that we have not discussed here (see Yvon, 1979 McCarley, 1982). For example, there are metal-cluster compounds such as the Chevrel phases, M,jMo6X8(X = S or Se) and condensed metal-cluster chain compounds such as TlMojScj, TijTe, NaMo O and M PtjO. TTF halides and TTF-TCNQ complexes (Section 1.9) constitute molecular mixed-valent systems in which the mixed valency is associated with an entire molecule the charge on TTF in such compounds is nonintegral. The structure of TTF-Br(, 79 and... 

It was mentioned earlier that the interstitial atoms in the octahedral void of a discrete cluster may also be transition metal instead of nonmetal atoms as, for example in [Gd6li2Fe]. [190] Octahedral clusters which are centered by a transition metal atom and condensed into chains (Pr4l5M) [191] and twin chains... 

Reentrant superconductivity was first discovered with ErRh4B4. [204] The chain of trans edge condensed M4 tetrahedra in which the coordinating atoms lie above all faces of the tetrahedra has been called a Tfetraederstern by Schubert. This very common feature links the structural chemistry of condensed cluster compounds with that of the intermetallic phases. [205]... 

In polyelectrolyte solutions, the counterion condensation on linear polyelectrolyte chains is known to occur when the charge density along the chain exceeds the critical value [40]. Our work indicates the existence of a critical value for the separation distance between chains, where the interchain interaction changes drastically, most likely due to the transition in the binding mode of the counterions (see Fig. 13). Many peculiar forms of behavior, which are often interpreted by the cluster formation or the interchain organization of polyelectrolytes, have been reported for high concentrations of aqueous polyelectrolytes... 

The cluster condensation can be carried on the chains of octahedra sharing edges can be joined to double-strands and finally to layers of octahedra (Fig. 13.18). Every layer consists of metal atoms in two planes arranged in the same way as two adjacent layers of atoms in a closest-packing of spheres. This is simply a section from a metal structure. The X atoms occupy positions between the metal layers and act as insulating layers. Substances like ZrCl that have this structure have metallic properties in two dimensions. 

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