Structural transitions in ice samples at low temperatures and pressures |
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Authors: | V. B. Efimov A. N. Izotov A. A. Levchenko L. P. Mezhov-Deglin S. S. Khasanov |
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Affiliation: | 1.Institute of Solid State Physics,Russian Academy of Sciences,Chernogolovka, Moscow region,Russia |
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Abstract: | The structure of ice samples formed in the decay of a water impurity gel at temperatures above 4 K and atmospheric pressure has been examined. The X-ray diffraction analysis indicates that three phases coexist in the initial sample at temperatures of 85–110 K. These phases are amorphous ice occupying up to 30% of the sample volume, cubic-phase ice I c metastable at low pressures (∼60%), and normal hexagonal ice I h (≤6%). The characteristic sizes of crystals of the cubic and hexagonal phases are about 6 and 30 nm, respectively. The amorphous phase at annealing above 110 K is gradually transformed to the crystalline phase both cubic and hexagonal. This transition is accompanied by two processes, including a fast increase in the sizes of cubicphase nanocrystals and the partial transition of the cubic phase I c to the hexagonal one I h. Hexagonal ice I h prevails in the bulk of the sample above 200 K. |
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