Time-of-flight neutron diffraction study on lithium dinitride iodide, Li 7N 2I

Abstract

The structure of Li 7N 2I has been redetermined from neutron diffraction data using the high resolution powder diffractometer (HRPD) at the spallation source ISIS, UK. The title compound crystallizes in the space group F4¯3m (No.216), a=1038.797(1) pm with eight formula units per unit cell. The Li 7N 2I-structure comprises a cationic Li 13N 4 staggered+ framework which is built of monocapped octahedra. While all Li atoms at the vertices are shared between two neighbouring units, the capping metal atom is shared by four octahedra. The Li 13N 4 staggered+ network is closely related to the B 2X 6 octahedral framework observed in the pyrochlore structure. Large voids in the structure are occupied by iodide and a Li +T ion pair. There is evidence that the nonsphericity of the Li +I − dipole induces a complicated Lidisorder in the Li-N framework.