A series of samples with decreasing Mg contents was prepared which exhibited diffraction patterns that contained the lines of Mg, plus a second phase. The latter increased in intensity, while the former decreased, as the composition, MgB2, was approached. The lines of the diffraction pattern which corresponded to the assumed compound were attributed to a primitive hexagonal cell with a = 3.084Å and c = 3.522Å. The density of the compound was 2.667g/cm3; implying one molecule per unit-cell. The overall structure was of AlB2-type, and the B-B distance in the hexagonal net was 1.780Å.

An X-Ray Study of the Magnesium Borides. V.Russell, R.Hirst, F.A.Kanda, A.J.King: Acta Crystallographica, 1953, 6, 870