New cubic cluster phases in the Mg–Ni–Ga system

• Published in: Acta crystallographica Section B, Structural science, crystal engineering and materials Structural science, crystal engineering and materials, 2020-08, Vol.76 (4), p.534-542
• Main Authors: Pavlyuk, Nazar, Dmytriv, Grygoriy, Pavlyuk, Volodymyr, Rozdzynska-Kielbik, Beata, Cichowicz, Grzegorz, Cyranski, Michał K., Chumak, Ihor, Ehrenberg, Helmut
• Format: Article
• Language: English
• Subjects: Apexes; chemical bonding; Clusters; Crystal structure; Crystals; electronic structure calculations; Encapsulation; Fullerenes; Gallium; Graph theory; icosahedral clusters; Icosahedrons; intermetallics; Nickel; single‐crystal methods
• ISSN: 2052-5206; 2052-5192; 2052-5206
• DOI: 10.1107/S2052520620006423

The crystal structure of new Mg9Ni6Ga14 and Mg3Ni2Ga compounds were investigated by single‐crystal diffraction. Both structures can be described as three‐core‐shell cluster compounds. In the Mg6Ni9Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene‐like truncated icosahedron, thus the three core–shell cluster [Ni6Ga6@Mg20@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg6] octahedron is encapsulated within the [Ni12Ga6] flattened icosahedron in vertices of which there are 12 nickel atoms, and six lateral edges are centered by gallium atoms, which in turn is encapsulated within a [Mg36] pseudo‐rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three‐shell cluster is [Mg6@Ni12Ga6@Mg36]. The crystal structures of two new Mg9Ni6Ga14 and Mg3Ni2Ga phases were determined using X‐ray diffraction and their chemical compositions were confirmed by electron probe microanalysis. The main common feature for both phases, besides being of cubic symmetry (), is that they form three‐shell clusters which close pack in crystal space.