Deuteron ordering in ice containing impurities; A Neutron diffraction study

Fukazawa, Hiroshi; Hoshikawa, Akinori; Yamauchi, Hiroki   ; Yamaguchi, Yasuo*; Igawa, Naoki   ; Ishii, Yoshinobu

We measured neutron diffraction of powdered samples of ice containing impurities (e.g., potassium deuteroxide, sodium deuteroxide) to analyze the formation of ice XI, a deuterium-ordered phase of ice, from ice Ih, a disordered phase. We found that the diffraction profiles changed with time for several days at 62-70 K, which are below the transition temperature = 76 K. From the Rietveld analysis of the diffraction profiles, we determined the change of the structural parameters with the phase transition. The structural analysis provides direct evidence for the existence of deuteron-ordered arrangements in ice containing impurities below . On the basis of the Rietveld analysis, we obtained the mass fraction () of ice XI as functions of time and temperature. We report a structural observation for the nucleation and growth of ice XI under various conditions (such as temperature variations and impurity effects), which leads to understand whether or not f reaches unity at an infinite annealing time.