Rhombohedral boron subnitride, B13N2, by X-ray powder diffraction

The structure of the title compound consists of distorted B-12 icosahedra linked by N - B - N chains. The compound crystallizes in the rhombohedral space group R (3) over barm ( No. 166). The unit cell contains four symmetry-independent atom sites, three of which are occupied by boron [ in the 18h, 18h ( site symmetry m) and 3b ( site symmetry (3) over barm) Wyckoff positions] and one by nitrogen ( in the 6c Wyckoff position, site symmetry 3m). Two of the B atoms form the icosahedra, while N atoms link the icosahedra together. The main feature of the structure is that the 3b position is occupied by the B atom, which makes the structure different from those of B6O, for which these atom sites are vacant, and B4+xC1-x, for which this position is randomly occupied by both B and C atoms.