NaK29Hg48: A Contradiction to or an Extension of Theoretical Concepts to Rationalize the Structures of Complex Intermetallics?
✍ Scribed by Hans-Jörg Deiseroth; Erik Biehl
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 401 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
NaK 29 Hg 48 is a new silver metallic, air-sensitive ternary alkali metal amalgam with metallic properties. It crystallizes in space group Pm3 n (No. 223, Z ؍ 2, a ؍ 1685.3(2) pm) and shows a superconducting phase transition at 2.5 K. Its crystal structure is characterized by novel icosahedral Hg 12 clusters centered by Na atoms and hexagonal antiprismatic Hg 12 clusters (99drums::) centered by K atoms. Both cluster types are embedded in a matrix of K atoms. With respect to the topology of the cluster centers the three-dimensional arrangement corresponds to the A15 structure type (Nb 3 Sn). The crystal structure of NaK 29 Hg 48 is closely related to that of the complex intermetallic phases A 3 Na 29 In 48 (A ؍ K, Rb, Cs) and others. It is an unexpected electron de5cient borderline case with respect to electron counting rules (Wade:s rules and Zintl+Klemm concept), which were successfully applied to explain the occurence of icosahedral and hexagonal antiprismatic In 12 /Tl 12 clusters in the latter two compounds.