STRUCTURAL REFINEMENT OF OLIVINE-TYPE LIMGASO4

The refinement of the LiMgAsO4 structure by powder neutron diffraction confirms that it is isostructural with olivine. The structure is orthorhombic, Pnma space group, with a = 10.4183(15), b = 5.9660(8), c = 4.8692(5) angstrom, and Z = 4. The lithium and magnesium atoms are fully ordered on the octahedral sites with average bond lengths [Li-O] = 2.187, [Mg-O] = 2.108 and [As-O] = 1.672 angstrom. LiMgAsO4 is isostructural with LiMgPO4 but not with LiMgVO4. However, a close structural relationship exists between the arsenate and the vanadate involving similar cation arrays but different anion arrays.