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Bringing Order to Large Scale Disordered Complex Metal Alloys: Gd2Au15-xSbx and BaAuxGa12-x


Two new tetragonal complex metallic alloys (CMAs) have been discovered and characterized: Gd2Au15-xSbx [x = 3.0-3.6; I4/mmm; tI34; a = 7.31-7.33 Å, c = 14.05-14.11Å; V = 750.2-758 Å3] and BaAuxGa12-x [x = 3.6−4.4; I4/mcm; tI104; a = 8.77−8.78 Å, c = 26.06−26.13 Å; V = 2006.5-2010Å3]. Both structures incorporate significant anionic site mixing and intricate positional disorder. Gd2Au15-xSbx represents a new structure type with in-plane disordered, however, strongly geometrically restricted rhombi motifs. These rhombi connect through additional mixed Au/Sb positions along the c axis forming octahedral fragments. BaAuxGa12-x finds its place within the extended NaZn13 structural family, displaying cation centered snub cubes with empty, distorted icosahedra (allowing for the 1:12 ratio) and tetrahedral stars. The split positions order due to geometric constraints to form nets of crown cyclooctane-like sheets in two different conformations. Adjacent planes adopt opposite conformations, forming layers of snub cubes with ordering between layers, but disordered across the greater structure. The substantial degree of mixing in both structures, together with mutual orientation of the ordered and disordered positions suggest a significant importance of heteroatomic bonding, typically found for polar intermetallic compounds.

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Publication details

The article was received on 26 Oct 2017, accepted on 28 Nov 2017 and first published on 28 Nov 2017

Article type: Paper
DOI: 10.1039/C7CE01865G
Citation: CrystEngComm, 2017, Accepted Manuscript
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    Bringing Order to Large Scale Disordered Complex Metal Alloys: Gd2Au15-xSbx and BaAuxGa12-x

    A. Mudring, C. Celania and V. Smetana, CrystEngComm, 2017, Accepted Manuscript , DOI: 10.1039/C7CE01865G

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