New Cubic Cluster Phases In The Mg-Ni-Ga System

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 Mg9Ni6Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg-20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene-like truncated icosahedron, thus the three core-shell cluster [Ni6Ga6@mg(20)@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg-6] 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 [Mg-36] pseudo-rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three-shell cluster is [Mg-6@Ni12Ga6@Mg-36].