METALLIC ZINTL PHASES IN RARE-EARTH-METAL TRELIDES. Jing-Tai Zhao¹ and John D. Corbett, Ames Laboratory and Iowa State University, Ames, IA50011, USA

The development of new solid state materials demands more and more understanding of properties as they related to structure. The Zintl-Klemm concepts[1] proved to be useful when dealing with the structure-bonding-property relationships of the so-called Zintl Phases. The breath of the applicability of these rules were explored to rare- earth-metal trelides with more polar character.

La₃In₅, Pu₃Pd₅-type, contains well-defined indium square pyramids In₅^9- (C_2v,d(In-In)~3.0-3.2Å) (the denoted charges here and thereafter have only formal meanings) with minimum intercluster separation of 3.43 and 3.58Å, which can be readily described as a close shell nido-deltahedron.

Y₃Ga₂, Gd₃Ga₂-type, contains isolated Ga^5- and single bounded dumbbell Ga₂^8- units.

YGa, CrB-type, contains single-bounded infinite zigzag chains [[infinity]] ¹[Ga^3-] (d(Ga-Ga)~2.56Å) with minimum interchain separation of >4.0Å.

All the above three compounds can be readily described structurally as Zintl phases and they are poorly metallic and Pauli-paramagnetic-like character[2].

The term "metallic Zintl phase" seems appropriate to describe compounds with structures containing tightly bound anion arrays in the classical limit, while with the weak metallic conduction resulted from the presence of some slightly delocalized electrons at the Fermi level.

[1] (a)Zintl, E. Angew. Chem.1939, 51, 1. (b)Klemm, W. & Busmann, E. Z. Anorg. Allg. Chem. 1963, 319, 297.

[2] (a)Zhao, J.-T. & Corbett, J.D. Inorg. Chem. 1994, 34, 378. (b) Zhao, J.-T. & Corbett, J.D. unpublished research.