Neutron diffraction study of hydrogen-ordered ice XI; Annealing effect and memory effect

Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B. C.*; Fukazawa, Hiroshi

We measured neutron diffraction profiles of KOD, NaOD, LiOD, Ca(OD), and ND-doped ices. Ice XI, which is a hydrogen-ordered phase of normal ice (ice Ih), was observed in the KOD and NaOD-doped ices although Ca(OD) and ND-doped ice did not transformed to ice XI. The mass fraction of ice XI to that of the doped ice () was estimated using Rietveld analysis for each doped ice. The value of the doped ice, which had once experienced being ice XI, was larger than that of the doped ice, which had never experienced being ice XI. The large value of the doped ice indicates that small hydrogen-ordered domains remained above the transition temperature between ice XI and Ih. Our results suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI. In this paper, we discussed the existence of the small hydrogen-ordered domains in space and the evolution of icy grain.