Preparation and crystal structure of lithium nitride hydride, Li4NH, Li4ND

Single phase Li4NH was prepared by the reaction of Li3N and LIH at 490 degrees C. Its structure has been solved from x-ray and time-of-flight neutron powder diffraction data. Li4NH crystallizes in an ordered variant of the Li2O structure. N and H occupy the sites of two interpenetrating "extended" diamond lattices. Li occupies all N2H2 tetrahedral voids and is found to be shifted into a N2H tetrahedral face. As a result H is in compressed tetrahedral coordination by Li, while N is in bisdisphenoidal coordination by Li. Alternatively, the Li4NH structure may be regarded as a [Li4N](+) threedimensional net, its voids being filled up with H-. Li4NH is a reactive solid, which decomposes to imide when in contact with N-2 or H-2 at some 400 degrees C.