Synthesis and crystal structure of MgB12Si2—The first ternary compound in the system B/Mg/Si

We report on the synthesis of MgB12Si2 the first ternary compound in the system B/Mg/Si. Yellow transparent single crystals were yielded from the elements at 1600 °C in h-BN crucibles welded in Ta ampoules. MgB12Si2 crystallizes orthorhombic in the space group Pnma with image, image, image and image. The crystal structure is characterized by layers of B12 icosahedra, connected by isolated Si atoms to a three-dimensional framework. Mg atoms are placed in voids of the framework. Each icosahedron forms 8 B–Si bonds and 4 exohedral B–B bonds. The Si atoms are tetrahedrally coordinated by B atoms of the B12 icosahedra.