Crystal structure of Hf6PtAl2 and comparison with HfPtAl

Some of the Hfd-metal-Al systems show the existence of intermetallic compounds with different superstructures of the Fe 2P type. Markiv et al. [1,2] found the equiatomic compound HfNiAl and the ternary compounds Hf 6MAl 2 (M = Fe, Co, Ni), which crystallize with the ZrNiAl and Zr 6CoGa2 (antiK2UF6) structure types, respectively. Both structures are ordered variants of the Fe 2P type (i.e. Fe (1) 3 Fe (2) 3 P (3) 2 P (4) 1 ): Al (1) 3 Zr (2) 3 Ni (3) 2 Ni (4) 1 for ZrNiAl and Zr (1) 3 Zr (2) 3 Ga (3) 2 Co (4) 1 for Zr6CoGa2. In our previous paper [3] we have shown that the related ZrPtAl and HfPtAl compounds belong to the HfRhSn type (i.e. Hf (1) 6 Sn (2) 6 Rh (3) 4 Rh (4) 2 ), a superstructure of Mg2Ga (i.e. Mg (1) 6 Mg (2) 6 Ga (3) 4 Ga (4) 2 ). The latter is a deformed variant of the ZrNiAl (Fe 2P) type [4]. In this paper we report the results of the crystal structur e investigation of a new compound, Hf 6PtAl2. For the purpose of comparison we also reinvestigated the structure of the HfPtAl intermetallic, which was synthesized under the same conditions as Hf 6PtAl2.