Intermetallic phases containing linked polyhedra

Triangular units are the building bloeks of the Wade clusters, but they are also present in the intermetallie phase BaSn3. This phase had been previously described as distorted hexagonal close packing in which the positions of each hexagonal layer is occupied in a 1 3 ratio by Ba and Sn atoms. The layers stack in an ABAB sequence as depicted in Fig. 5, Distortion of the Sn atoms within 

Three-dimensional linked polyhedra are frequently found in solids that are rich in E elements. The clathrate-type structures NasSi46 (clathrate-I) and Na cSii36 (clath-rate-II, 3 x have been known for many years. Further examples of the 

K5Pb24 crystallizes in the a-Mn structure type (Pearson symbol cIP58) ° , where 5 of 29 positions are occupied by potassium. The Pb network can be described by 

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