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Synthese und Kristallstrukturen ternärer Phosphide und Arsenide des Rhodiums und Iridiums

2002; Wiley; Volume: 628; Issue: 3 Linguagem: Alemão

10.1002/1521-3749(200203)628

1521-3749

A. Wurth, Anke Löhken, Albrecht Mewis,

Iron-based superconductors research

Von acht neuen Verbindungen wurden Einkristalle durch Erhitzen der entsprechenden Elementgemenge in einer Bleischmelze gezüchtet und röntgenographisch untersucht. Ca2Ir12P7 (a = 9, 512(1), c = 3, 923(1) Å) ist ein weiterer Vertreter des Zr2Rh12P7-Typs, das Vorliegen von Mikrodomänen erforderte die Verfeinerung der Strukturparameter in der Raumgruppe P63/m. Ca5Rh19P12 (a = 12, 592(1), c = 3, 882(1) Å) und Ca5Ir19P12 (a = 12, 577(2), c = 3, 954(1) Å) kristallisieren im Ho5Ni19P12-Typ (P6¯2m; Z = 1), während die Verbindungen A6Rh30X19 eine geringfügig modifizierte Yb6Co30P19-Struktur bilden (Gitterkonstanten s. Abstract). Da eines der vier kristallographisch unterschiedlichen Nichtmetallatome entlang [001] fehlgeordnet ist, was zur Bildung von Mikrodomänen führt, wurden die Strukturparameter nicht in der Raumgruppe P6¯ (Yb6Rh30P19-Typ), sondern in P63/m verfeinert. Das Metall:Nichtmetall-Verhältnis liegt bei den Verbindungen im Bereich von 2:1. Dementsprechend sind die Nichtmetallatome größtenteils von neun Metallatomen in Form seitenüberkappter trigonaler Prismen koordiniert, die auf unterschiedliche Art und Weise miteinander verknüpft sind. Ternary Phosphides and Arsenides of Rhodium and Iridium: Synthesis and Crystal Structures Single crystals of eight new compounds were prepared by heating mixtures of the elements in a lead flux. They were investigated by X-ray methods. Ca2Ir12P7 (a = 9.512(1), c = 3.923(1) Å)is an additional representative of the Zr2Rh12P7 type structure, micro domains required refinements of the structural parameters in space group P63/m. Ca5Rh19P12 (a = 12.592(1), c = 3.882(1) Å) and Ca5Ir19P12 (a = 12.577(2), c = 3.954(1) Å) crystallize with the Ho5Ni19P12 type structure (P6¯2m; Z = 1), whereas the compounds A6Rh30X19 form a slightly modified structure of the Yb6Co30P19 type. The lattice constants are: Ca6Rh30P19: a = 15.532(1) Å, c = 3.784(1) Å Sr6Rh30As19: a = 16.135(2) Å, c = 3.916(1) Å Eu6Rh30P19: a = 15.566(1) Å, c = 3.821(1) Å Eu6Rh30As19: a = 16.124(1) Å, c =5 3.903(3) Å Yb6Rh30P19: a = 5 15.508(1) Å, c =5 3.770(1) Å Because one of the four non-metal atoms, located on different crystallographic sites, is disordered along [001] micro domains are formed. Therefore the parameters were not refined in space group P6¯ (Yb6Rh30P19 type), but in space group P63/m. The metal:non-metal ratio of all compounds is in the range of 2:1. Accordingly most of the non-metal atoms are coordinated by nine metal atoms, which form tricapped trigonal prisms. These polyhedra are combined with each other in a different way.