Synthesis and crystal structure of Na2LiAlD6

Na2LiAlD6 was synthesized by ball milling of NaAlD4 and LiAlD4 with subsequent heat treatment under D2 pressure. The compound has an ordered perovskite-type structure with Li and Al in octahedral positions. The [LiD6]3- and [AlD6]3- complex anions are ordered in three dimensions such that the neighbouring octahedron is of different type in all three directions. Each octahedron shares each corner with one other octahedron. Na2LiAlD6 crystallizes in the cubic space group Fm3-bar m with unit-cell dimension a=7.38484(5)A. The structure may also be described as a c.c.p. geometry of (isolated) AlD6 entities with Li filling the octahedral sites and Na filling all the tetrahedral sites. Sodium is connected to three D atoms from each of the four surrounding AlD6 octahedra, resulting in a total coordination number of 12