Neutron structure refinement of γ- and β-lithium lodate: Comparison between α, γ, and β phases

Abstract

Neutron powder diffraction patterns of (γ + α) and β lithium iodate samples are used to refine the structure of γ (at 488 K) and β (at 513 K) LiIO 3. All three modifications are built up from Li + and (IO 3) − pyramids but lithium is six-, five-, and fourfold-coordinated to oxygen in the α-, γ-, and β-phases, respectively. The study of IO 3 group displacements through the α → γ phase transition suggests that the γ phase structure is closely related to a mixed orthohexagonal description of the α structure where both enantiomorphic forms of the hexagonal unit cell are present. The existence of a new α′ modification is postulated in view of neutron diffraction and NMR results. A simulation of the structure of hexagonal α-LiIO 3 is also presented.