A determination of the crystal structure of ice XI

Abstract

Below 72 K ice doped with KOH transforms to an ordered phase known as ice XI. A powdered sample of such doped ice annealed for several days below 72 K was studied by neutron diffraction and found to be a two-phase mixture of ice Ih and ice XI. The ice XI has an orthorhombic unit cell, and the diffraction profile is consistent with the predicted Cmc21 structure.