The alumosilicide HoAl2.8Si0.2

Abstract

The holmium alumosilicide HoAl 2.8 Si 0.2 was synthesized by arc melting and subsequent annealing at 600ºC. Its crystal structure was studied by X-ray powder diffraction and identified as BaPb 3 type: Pearson symbol hR36, space group R-3m, a = 6.12537(7), c = 20.9526(3) Å. The structure is close-packed and consists of oneatom thick close-packed layers of composition Ho(Al,Si) 3 in h 2 c stacking, with 9 layers in the translation period along [001]. The coordination polyhedra are cuboctahedra (sites Ho2 and M2) and anticuboctahedra (sites Ho1 and M1). For the Ho atoms the coordination polyhedra are built up exclusively of Al/Si atoms, whereas for the latter the composition of the polyhedra is Ho 4 M 8 .