Single-Crystal Neutron Diffraction Studies of the Structure of Ice XI

Abstract

Single crystals of KOH-doped ice Ih, transformed into the low-temperature ordered phase known as ice XI, have been studied by neutron diffraction. High-resolution measurements show a splitting of the 00l diffraction peaks into an ice XI and a residual ice Ih component, with about 37% transformation to ice XI. New diffraction peaks from the ice XI have been measured. These are consistent with a ferroelectrically ordered structure with space group Cmc21.