Existence of ferroelectric ice in the Universe; A Neutron diffraction study

Fukazawa, Hiroshi

Water molecules are dipolar, and neutron diffraction studies provide evidences that ices VIII and IX (the proton ordered phases of ices VII and III) exist as stable low-temperature phases at high pressure. However, under an atmospheric pressure, the proton of "normal" ice Ih is disordered even though a very low temperature. A question that has long fascinated researchers is whether there is an existence of ferroelectric water ice (FWI) named ice XI as a stable phase under an atmospheric pressure, which caused by aligned water molecules (i.e., the proton ordering). The old debate is implicated in our understanding of condensed matter, and recently the ferroelectricity in ice and clathrate hydrates (some hydrates also have the proton ordering) becomes an earnest subject: "FWI" exists on outer planets, such as Pluto ? On the basis of neutorn diffraction study, we discusse the structures of ices which form icy planets, such as Pluto and Charon.