High three clusters

Figure 7.11 Some basic types of roll arrangements (a) two-high, (b) three-high, (c) four-high, (d) cluster, (e) tandem rolling with three stands, and (f) planetary milling. McGraw-Hill Encyclopedia of Science and Technology, Vol. 11, 8th ed., p. 54. Copyright 1997 by McGraw-HiU.

In 1943, Hieber and Lagally reported that the reaction of anhydrous rhodium trichloride with carbon monoxide at 80°C, under pressure, and in the presence of silver and copper as halogen acceptors, gave a black crystalline product which, on the basis of elemental analysis, was formulated as Rh4(CO)n 75). The exact nature of this compound was established 20 years later by Dahl using three-dimensional X-ray analysis which led to its reformulation as Rh6(CO)i6 53). This discovery can be regarded as the birthday of the chemistry of high nuclearity clusters. 

In addition to meteorites, three other important types of extraterrestrial material are available for analysis interplanetary dust particles (IDPs), micrometeorites, and Stardust samples. Interplanetary dust particles are collected in the stratosphere by high-altitude research aircrafts. Most of these samples are smaller than 20 pm in diameter, although some of the highly porous cluster particles probably exceeded... 

Mingos has recently developed an electron counting procedure (which may be described as Polyhedral Inclusion ) which is based on the formal division of the high nuclearity cluster into an internal (encapsulated) polyhedron and an external (surface) polyhedron128. Three sub-classes of close-packed cluster have been identified ... 

The binary indium-rich transition metal compounds show a variety of different indium networks. In the structures of T2lns (T = Ti, Hf), the indium atoms form infinite two-dimensional (2D) planar networks, which can be described as a tessalation of triangles, squares, and pentagons. The 2D network is also found in the structures of the Lasins compounds, which contain well-defined indium square pyramids and some intercluster indium-indium distances that are only 11-15% greater than the average intracluster bond lengths. The apparent Ins " cluster in Lasins can be described as a closed shell nido-deltahedron, and the compound structurally as a Zintl phase. The /S-Ysins compounds with a similar structure to Lasins present a slow first-order phase transition to a-YsIns at high temperature. Clusters in the low-temperature a-YsIns phase are twisted and Joined by short bonds at trans-basal positions into chains that are more weakly interconnected into a three-dimensional structure. 

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