Crystal structure of the rare earth borosilicide Er 8Si 17B 3

Abstract

The ternary borosilicide Er 8Si 17B 3 has been prepared by tin flux. Its crystal structure has been determined from X-ray single crystal intensity data: space group Cmc2 1 , Z=1; a=4.0128(2) Å, b=28.8674(16) Å and c=3.8413(2) Å; R=0.029 ( Rw=0.034); 540 independent reflections; 44 variable parameters. The structure of a new type is derived from the AlB 2-type with a partial order on the metalloı̈d sublattice. The salient characteristic results from the occupancy by metalloid atoms of the tetrahedra and pyramids formed by erbium atoms, which are arranged at the interface of the AlB 2 slabs. Finally, this structure is discussed in detail with the AlB 2 derivative structure types Ho 3Si 4 and ErGe 1.83.