The new ternary gallide MgMn4Ga18 (magnesium tetramanganese octadecagallium) was synthesized and its crystal structure determined by means of single-crystal X-ray diffraction. The MgMn4Ga18 structure can be described as that of a three core-shell cluster compound. The Mg atoms are surrounded by 16 adjacent Ga atoms, [MgGa16], and the respective coordination polyhedron is an octadecahedron. This [MgGa16] octadecahedron is encapsulated inside a [Ga32] icohexahedron, which is in turn encapsulated inside a [Ga40] pentacontaoctahedron. As a result, a three core-shell cluster, [MgGa16@Ga32@Ga40], is identified. Electronic structure calculations were performed by means of the TB-LMTO-ASA program and additionally confirm the existence of the core-shell packing of the clusters.
Keywords: chemical bonding; core–shell cluster; crystal structure; electronic structure; ternary gallide.