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 R3m (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 3m) 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 B(6)O, for which these atom sites are vacant, and B(4+x)C(1-x), for which this position is randomly occupied by both B and C atoms.