X-ray diffraction measurements up to momentum transfer q=16 Å−1 were performed at atmospheric pressure on both the high-density form of amorphous ice obtained by pressurization of crystalline ice Ih at 77 K up to 2 GPa and the low-density form obtained by further heating. These two amorphous phases exhibit significant differences at the level of the second- and third-nearest neighbors which involve a decrease of the O–O–O angle on compression at high pressure. Moreover, it is found that the low-density form is quite similar to that obtained by vapor deposition on cooled substrates at 77 K.

No abstract

X-ray diffraction experiments on water confined in silica gel powder hydrated at 22% and 50% and in vycor glass hydrated at 25% are presented and analyzed at room temperature and down to 77 K. At room temperature, the molecular packing at the level of the first neighbors is found similar to that in bulk water, but a distortion is observed at the level of the second neighbors. At low temperature, the intensity of water confined in silica gel powder show evidence for the simultaneous presence of cubic ice and uncrystallized water.

No abstract

No abstract