Synthesis and structure of K3N

Two phases in the binary system K/N have been obtained via co-deposition of potassium and nitrogen onto polished sapphire at 77 K and subsequent heating to room temperature. The powder diffraction pattern of one of these phases can be satisfactorily interpreted by assuming the composition K3N, and the anti-TiI3 structure-type, which is also adopted by Cs3O. The resulting hexagonal lattice constants are: a = 779.8(2), c = 759.2(9) pm, Z = 2, P6(3)/mcm. Comparison with possible structures Of K3N generated by computational methods and refined at Hartree-Fock- and DFT level, reveals that the energetically most favoured structure has not formed (presumable Li3P-tyPe), but instead one of those with very low density. In this respect, the findings for K3N are analogous to the results on Na3N. The thermal evolution of the deposited starting mixture has been investigated. Hexagonal K3N transforms to another K/N phase at 233 K. Its XRD can be fully indexed resulting in an orthorhombic cell a = 1163, b = 596, c = 718 pm. Decomposition leaving elemental potassium as the only residue occurs at 263 K.