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

The structure of the title compound consists of distorted B12 icosa­hedra linked by N—B—N chains. The compound crystallizes in the rhombohedral space group R\overline{3}m (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 \overline{3}m) 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.