Crystal structures and phase transformation of deuterated lithium imide, Li2ND

Abstract We have investigated the crystal structure of deuterated lithium imide, Li 2 ND, by means of neutron and X-ray diffraction. An order–disorder transition occurs near 360 K. Below that temperature Li 2 ND can be described to the same level of accuracy as a disordered cubic ( F d 3 ¯ m ) structure with partially occupied Li 32e sites or as a fully occupied orthorhombic ( Ima 2 or Imm 2) structure. The high temperature phase is best characterized as disordered cubic ( F m 3 ¯ m ) with D atoms randomized over the 192l sites. Density functional theory calculations complement and support the diffraction analyses. We compare our findings in detail with previous studies.