Reindarstellung und Kristallstruktur von Lithiumtrinitridbromid, Li10N3Br / Preparation and Crystal Structure of Lithium Trinitride Bromide Li10N3Br

Abstract

Li10N3Br has been prepared by the reaction of Li3N and dry, OH-free LiBr. It is found to be the most nitride rich compound in the quasi-binary system Li3-2xN1-xBrx. The previously unknown structure of the title compound has been solved from neutron powder diffraction data recorded using the flat-cone and powder diffractometer E2 at the Berlin BER II reactor. Li10N3Br crystallizes in the hexagonal space group P6̄m2 (No. 187), a = 741.3(1) pm, c = 386.57(3) pm, with one formula unit per unit cell. The structure is closely related to Li3N (space group P6/m m m , a = 364.8(1) pm, c = 387.5(1) pm). It comprises roughly pentagonal bipyramidal Li7N units which share edges and vertices to give a three-dimensional Li10N 3 network. The Li atoms in axial positions are in an almost linear coordination with the central N atom. The Li atoms in the equatorial positions are surrounded either by N atoms in an ideal trigonal coordination or by N and Br atoms in a distorted tetrahedral coordination. The Br atoms are situated in the large trigonal prismatic holes formed by the Li atoms.