Acta Crystallographica Section C

Structural Chemistry

Volume 70, Part 4 (April 2014)


inorganic compounds



Acta Cryst. (2014). C70, 355-358    [ doi:10.1107/S205322961400566X ]

MgAuGa and MgAu2Ga: first representatives of the Mg-Au-Ga system

V. Smetana, J. D. Corbett and G. J. Miller

Abstract: MgAuGa (magnesium gold gallium), the first ternary representative of the Mg-Au-Ga system, crystallizes in the space group P\overline{6}2m and adopts the Fe2P structure type (Pearson symbol hP9). Various phases with the general composition AB2 have been reported in the surrounding binary systems, viz. Mg2Ga (hP18), MgGa2 (hP6; CaIn2 type), AuGa2 (cF12; CaF2 type), Au2Ga (oS24; Pd2As type) and Mg2Au (oP12; Co2Si type). In principle, MgAuGa can be obtained from each of them by partial replacement of the major element with the missing element. In fact, the structure of MgAuGa closely resembles hexa­gonal Mg2Ga through a direct group-subgroup relationship. MgAu2Ga (magnesium digold gallium) also crystallizes hexa­gonally in the space group P63/mmc and is isotypic with Na3As. It adopts the structure of another binary compound, viz. Mg3Au (hP8), but shows an unexpected distribution of Mg, Au, and Ga among the atomic positions of the asymmetric unit. Both MgAuGa and MgAu2Ga can be described as formally anionic Au/Ga frameworks, with pseudo-hexa­gonal tunnels around Mg in MgAuGa or cages in MgAu2Ga.

CCDC references: 991455 and 991456

Formula: MgAuGa and MgAu2Ga

Keywords: crystal structure; ternary phase; Mg-Au-Ga system; Fe2P structure type; hexa­gonal Na3As structure type; MgAuGa; MgAu2Ga.


hkldisplay filedownload file

Structure factor file (CIF format) (19.8 kbytes)
[ doi:10.1107/S205322961400566X/ku3126Isup2.hkl ]
Contains datablock I


hkldisplay filedownload file

Structure factor file (CIF format) (7.4 kbytes)
[ doi:10.1107/S205322961400566X/ku3126IIsup3.hkl ]
Contains datablock II


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